Magnetic recording medium, and manufacturing method for the same

ABSTRACT

The present invention provides a method for manufacturing a magnetic recording medium comprising the steps of forming a carbon protective film onto a disc, the non-magnetic substrate of which is layered with a non-magnetic base film and magnetic film, using a reactant gas containing carbon atoms as a starting material, according to a plasma CVD method, wherein a mixed gas of hydrocarbon and hydrogen, in which the mixing ratio of hydrocarbon to hydrogen is in the range of  2  to  1˜1  to  100  by volume, is used as a reactant gas, during bias applying to said disc In addition, the present invention provides a magnetic recording medium comprising a carbon protective film formed onto a disc, the non-magnetic substrate of which is layered with a non-magnetic base film and magnetic film, wherein said carbon protective film is formed according to a plasma CVD method, while applying bias

TECHNICAL FIELD

[0001] The present invention relates to a magnetic recording medium suchas a magnetic disc and the like for use in magnetic disc devices, and amanufacturing method for the same.

RELEVANT ART

[0002] In recent years, in the field of magnetic recording, particularlywith respect to magnetic discs, remarkable improvements in the recordingdensity have been achieved. In particular, recent improvements in therecording density have continued at a phenomenal pace, achieving ratesof approximately 100 times in 10 years Technologies supporting theimprovement of recording density vary widely, however, one of the keyconcepts that can be mentioned is the technology of controlling thesliding characteristics between the magnetic head and magnetic recordingmedium

[0003] Sliding of the head on the medium is unavoidable ever since theintroduction of the CSS (Contact—Start—Stop) mode which is so-called“Winchester format” as the main mode for hard disc drives, wherein thebasic operation comprises the steps of sliding into contact, headflotation, and sliding into contact between the magnetic head andmagnetic recording medium. Accordingly, problems relating to tribologybetween head and medium have become critical technical problems Thus,properties such as resistance to abrasion and resistance to sliding overthe surface of the magnetic recording medium comprise the keys to areliable product, and efforts continue to develop and improve theprotective film, lubricating film, and the like, which coat the magneticfilm As a protective film for magnetic recording medium, filmscomprising various materials have been proposed However, from theperspective of the total performance such as coating performance anddurability, carbon films are principally employed

[0004] These carbon films are generally formed according to aspatter-coating method, in which the coating conditions are extremelyimportant due to their direct impact on resistance to corrosion and CSSproperties.

[0005] In addition, in order to improve the recording density, it ispreferable to reduce the flying height of the head, to increase thenumber of rotations of the medium, and the like. Thus, a superiorresistance to sliding is required for the magnetic recording medium. Onthe other hand, in order to improve the recording density by means ofreducing spacing loss, it's preferable to make the protective filmthinner, for example to a thickness of 100 Å or less. Hence, a thin,smooth and durable protective film is highly desired.

[0006] However, a carbon protective film formed according to theconventional spattering coating method, can sometimes lack durability,when the film is made thin, for example 100 Å or less

[0007] Therefore, a plasma CVD method is currently being studied as amethod for providing a carbon protective film with greater strength,compared to that produced by means of the spatter-coating method Thisplasma CVD method is disclosed in, for example, Japanese PatentApplication, Second Publication No. Hei 7-21858; First Publication LaidOpen No 7-73454; and the like

[0008] However, under the current demands for increased recordingdensity, it is difficult, from the perspective of durability to sliding,to produce a thin protective film to the point where a sufficiently highrecording density is achieved without lowering the output properties,according to the aforementioned conventional technology In addition, theconventional technology poses the problem of low coating rate, which inturn leads to production inefficiency.

[0009] In consideration of the aforementioned, the objectives of thepresent invention are described as follows.

[0010] (1) To provide a magnetic recording medium and manufacturingmethod thereof, that is reliable and capable of providing a sufficientlyhigh recording density, without lowering the output properties

[0011] (2) To provide a method for manufacturing the aforementionedmagnetic recording medium in an efficient manner

DISCLOSURE OF THE INVENTION

[0012] The method for manufacturing a magnetic recording mediumaccording to the present invention comprises a method for manufacturinga magnetic recording medium by means of forming a carbon protective filmonto the disc, the non-magnetic substrate of which is layered with anon-magnetic base film and magnetic film, using a reactant gascontaining carbon atoms as a starting material, according to a plasmaCVD method, wherein a mixed gas of hydrocarbon and hydrogen, in whichthe mixing ratio of hydrocarbon to hydrogen is in the range of 2 to 1˜1to 100 by volume, is used as a reactant gas, while applying a bias tosaid disc.

[0013] The aforementioned hydrocarbon preferably comprises at least onetype of hydrocarbon selected from among lower saturated hydrocarbons,lower unsaturated hydrocarbons, and lower cyclic hydrocarbons, and morepreferably comprises toluene

[0014] In the case of using toluene, toluene and hydrogen are mixed,with a mixing ratio of toluene to hydrogen preferably in the range of 1to 15˜1 to 20 by volume

[0015] The bias applied to the disc is preferably a high frequency bias

[0016] In addition, formation of a carbon protective film is preferablycarried out under high frequency electrical discharge.

[0017] When forming a carbon protective film on both sides of the discat the same time, it is preferable to make the phases of electricalpower supplied to each electrode arranged on the respective sides of theaforementioned disc different from each other The phase difference ofelectrical power supplied to each electrode is preferably in the rangeof 90˜270°, and in particular, more preferably the opposite phase (i.e ,180°)

[0018] The method for manufacturing a magnetic recording mediumaccording to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming a carbonprotective film onto the disc the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, wherein pulse D.C. bias having a frequency of 1kHz˜100 GHz and pulse width of 1 ns˜500 μs is applied to the disc, whenforming (during formation of) the carbon protective film

[0019] The frequency of the pulse D.C. bias applied to the disc ispreferably in the range of 10 kHz˜1 GHz, and the pulse width ispreferably in the range of 10 ns˜50 μs.

[0020] The average voltage of the pulse D.C. bias applied to the disc ispreferably in the range of −400˜−10 V.

[0021] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume The hydrocarbon preferablycomprises at least one type of hydrocarbon selected from among lowersaturated hydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons,

[0022] The magnetic recording medium according to the present inventionis provided with a carbon protective film onto the disc, thenon-magnetic substrate of which is layered with a non-magnetic base filmand magnetic film, that can be formed according to a plasma CVD methodwhile applying pulse D.C bias having a frequency of 1 kHz˜100 GHz andpulse width of 1 ns˜500 μs to the disc

[0023] The method for manufacturing a magnetic recording mediumaccording to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming a carbonprotective film onto the disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, wherein the temperature of the disc is heated to100˜250° C. prior to forming the aforementioned carbon protective film

[0024] The temperature of the disc is preferably in the range of150˜200° C.

[0025] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume, wherein the hydrocarbon mixedinto the reactant gas preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons

[0026] The pressure of the reactant gas is in the range of 0 1˜10 Pa,and preferably 2˜6 Pa, when forming the carbon protective film in themethod for manufacturing a magnetic recording medium according to thepresent invention

[0027] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume, wherein the hydrocarbon mixedinto the reactant gas preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons.

[0028] The method for manufacturing a magnetic recording mediumaccording to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming a carbonprotective film onto the disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, wherein the reactant gas is a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume, into which nitrogen gas isadded at a adding volume of 0.1˜100% of the mixed gas

[0029] The aforementioned hydrocarbon preferably comprises at least onetype of hydrocarbon selected from among lower saturated hydrocarbons,lower unsaturated hydrocarbons, and lower cyclic hydrocarbons.

[0030] The magnetic recording medium according to the present inventionmay comprise a non-magnetic substrate, layered with a non-magnetic basefilm, magnetic film, carbon protective film, and lubricating film;wherein said carbon protective film comprises a plasma CVD carbon layerformed according to a plasma CVD method, and a spatter carbon layerformed according to a spattering coating method, which lies in contactwith the lubricating film.

[0031] The thickness of the spatter carbon layer is in the range of5˜100 Å, and preferably 30˜100 Å, and the thickness of a plasma CVDcarbon layer is preferably In the range of 30˜100 Å.

[0032] In addition, the method for manufacturing a magnetic recordingmedium may comprise the steps of forming (1) a plasma CVD carbon layer,using a reactant gas containing carbon atoms as a starting material,according to a plasma CVD method, (2) a spatter carbon layer thereon,using a spatter gas, according to a spatter-coating method, and (3) alubricating film thereon, which lies in contact with said spatter carbonlayer

[0033] The reactant gas used for forming a plasma CVD carbon layeraccording to a plasma CVD method is preferably a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume, wherein the hydrocarbonpreferably comprises at least one type of hydrocarbon selected fromamong lower saturated hydrocarbons, lower unsaturated hydrocarbons, andlower cyclic hydrocarbons.

[0034] The spatter gas used for forming a spatter carbon layer accordingto the spatter-coating method is preferably argon, into which at leastone gas selected from among nitrogen, hydrogen, and methane, is added ata mixing ratio to the argon of 0.1˜100% by volume.

[0035] In addition, the method for manufacturing a magnetic recordingmedium according to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming a carbonprotective film on a disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, and lubricating film thereon, which lies incontact with the carbon protective film, wherein said films are formedwhile performing bias applying to the disc, with subsequent films formedwithout bias applying to the disc

[0036] The bias applied to the disc is preferably a pulse D C bias of−400˜−10 V, or a high frequency bias of 10˜300 W

[0037] The thickness of the carbon layer which is formed without biasapplying to the disc is preferably in the range of 5˜20 Å.

[0038] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen, with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume, wherein the hydrocarbonpreferably comprises at least one type of hydrocarbon selected fromamong lower saturated hydrocarbons, lower unsaturated hydrocarbons, andlower cyclic hydrocarbons.

[0039] In addition, the magnetic recording medium according to thepresent invention may comprise a carbon protective film and alubricating film on a disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, wherein thecarbon protective film comprises a first carbon layer, that is formedaccording to a plasma CVD method while performing bias applying to thedisc, and a second carbon layer, which lies in contact with thelubricating film, that is formed according to a plasma CVD methodwithout bias applying to the disc.

[0040] The thickness of the second carbon layer is preferably in therange of 5˜20 Å.

[0041] In addition, the magnetic recording medium according to thepresent invention may comprise a non-magnetic base film, magnetic film,protective film, and lubricating film on the non-magnetic substrate,wherein the protective film comprises a carbon layer, principallycomprising carbon, on a tantalum nitrogen layer, comprising tantalum andnitrogen with a mixing ratio of nitrogen of 1˜30% atm, with said carbonlayer being formed according to a plasma CVD method, and lying incontact with the lubricating film.

[0042] The thickness of the carbon layer is preferably in the range of5˜100 Å, while the thickness of the tantalum nitrogen layer ispreferably 1˜95 Å.

[0043] The method for manufacturing a magnetic recording mediumaccording to the present invention may comprise the steps of forming (1)a non-magnetic base film and magnetic film on a non-magnetic substrate,(2) a tantalum nitrogen layer thereon, which comprises a materialcontaining nitrogen and tantalum, with a mixing ratio of nitrogen of1˜30% atm; (3) a carbon layer thereon, which is formed according to aplasma CVD method, using a reactant gas containing carbon atoms, and (4)a lubricating film thereon, which lies in contact with the carbon layer

[0044] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen with a mixing ratio of hydrocarbon to hydrogenin the range of 2 to 1˜1 to 100 by volume. The hydrocarbon preferablycomprises at least one type of hydrocarbon selected from among lowersaturated hydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons.

[0045] In addition, the method for manufacturing a magnetic recordingmedium according to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming (1) anon-magnetic base film and magnetic film, (2) a carbon film thereon,using a reactant gas containing carbon atoms as a starting material,according to a plasma CV) method; and subsequently (3) a lubricatingfilm on the carbon protective film, wherein the surface of the carbonprotective film is irradiated with ultraviolet rays before forming thelubricating film

[0046] The wavelength of the ultraviolet rays irradiating the carbonprotective film is preferably in the range of 100˜400 nm, and the sourceof the ultraviolet rays is preferably an excimer emission lamp.

[0047] Additionally, the surface of the carbon protective film ispreferably washed, using water, before forming the lubricating filmthereon.

[0048] The aforementioned reactant gas preferably comprises a mixed gasof hydrocarbon and hydrogen, with a mixing ratio of hydrocarbon tohydrogen in the range of 2 to 1˜1 to 100 by volume. The hydrocarbonpreferably comprises at least one type of hydrocarbon selected fromamong lower saturated hydrocarbons, lower unsaturated hydrocarbons, andlower cyclic hydrocarbons.

[0049] In addition, the method for manufacturing a magnetic recordingmedium may comprise a method for manufacturing a magnetic recordingmedium by means of forming (1) a non-magnetic base film and magneticfilm, (2) a carbon film thereon, using a reactant gas containing carbonatoms as a starting material, according to a plasma CVD method; andsubsequently (3) a lubricating film on the carbon protective film;wherein the surface of the carbon protective film is washed, usingwater, before forming the lubricating film thereon

[0050] When washing the carbon protective film, the cleaning water usedpreferably comprises water of a high purity.

[0051] In addition, the magnetic recording medium according to thepresent invention may comprise a non-magnetic base film, magnetic film,carbon protective film, and lubricating film on a non-magneticsubstrate, wherein the carbon protective film is formed according to aplasma CVD method, followed by irradiation of the surface of the carbonprotective film with ultraviolet rays.

[0052] Additionally, the magnetic recording medium according to thepresent invention may comprise a non-magnetic base film, magnetic film,carbon protective film, and lubricating film on a non-magneticsubstrate, wherein the carbon protective film is formed, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, and the lubricating film principally comprisesat least one chemical compound represented by the following formula (1)through (5), the number average molecular weights of which lie in therange of 500˜6000

[0053] [wherein, m, n, p, q, r, s, t, u, v, and w each represents aninteger]

[0054] Additionally, the lubricating film may principally comprise amixture, which is formed by means of adding a chemical compoundrepresented by the following formula (6), into the aforementionedchemical compound, at a mixing ratio 0.1˜20%/ by weight.

[0055] [wherein, x represents an integer between 0 and 6]

[0056] Among the aforementioned, in particular, a lubricating filmprincipally comprising a compound represented by the aforementionedformula (1) or (5), the number average molecular weights of which lie inthe range of 500˜6000, is preferred

[0057] In addition, the aforementioned magnetic recording medium maycomprise a non-magnetic base film, a magnetic film containing Co, and acarbon protective film formed according to a plasma CVD method, on anon-magnetic substrate, wherein the extraction amount of Co is nogreater than 3 ng/cm² with respect to the area of the substrate, andpreferably no greater than 2 ng/cm², and more preferably, no greaterthan 1.5 ng/cm²

[0058] In addition, the method for manufacturing a magnetic recordingmedium according to the present invention may comprise a method formanufacturing a magnetic recording medium by means of forming (1) anon-magnetic base film and magnetic film on a non-magnetic substrate,and (2) a carbon protective film thereon, using a reactant gascontaining carbon atoms as a starting material, according to a plasmaCVD method, wherein the surface of the non-magnetic substrate is treatedwith texture-processing to form an average roughness (Ra) of the surfaceof the non-magnetic substrate is 1˜20 Å

[0059] When texture-processing the surface of the non-magnetic substratein the aforementioned manner, the average roughness of the surface ismore preferably in the range of3˜10 Å

[0060] The method for texture-processing is preferably a mechanicalmethod for texture-processing, in which abrasive particles are used,preferred examples of which may include processes in which the averageparticle diameter is 0.1˜0.5 μm.

[0061] The method for mechanical texture-processing is a method fortreating the surface of the non-magnetic substrate withtexture-processing, by means of rotating the non-magnetic substratewhile At the same time running an abrasive tape over the substrate incontact with the surface of the non-magnetic substrate, and supplyingabrasive particles between the abrasive tape and non-magnetic substrate.In this method, it is preferable to oscillate the abrasive tape in adirection which crosses the aforementioned running direction, at afrequency of 0.1˜5 Hz.

[0062] The rotational speed of the non-magnetic substrate whenperforming texture-processing is preferably in the range of 300˜2000 rpm

[0063] The aforementioned reactant gas is preferably a mixed gas ofhydrocarbon and hydrogen, wherein the hydrocarbon preferably comprisesat least one type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons

[0064] In addition, the magnetic recording medium according to thepresent invention may comprise a non-magnetic base film, magnetic film,and carbon protective film, which are formed on the non-magneticsubstrate according to a plasma CVD method, wherein the average surfaceroughness (Ra) of the non-magnetic substrate is in the range of 1˜20 Å.

[0065] In addition, the method for manufacturing a magnetic recordingmedium according to the present invention is a method for manufacturinga magnetic recording medium by means of forming a carbon protective filmon a disc, the non-magnetic substrate of which is layered with anon-magnetic base film and magnetic film, using a reactant gascontaining carbon atoms as a starting material, according to a plasmaCVD method, wherein bias applying is performed to the disc at the timeof forming the carbon protective film, and the reactant gas is eitherbutadiene gas or a mixed gas of butadiene and hydrogen comprising amixing ratio of butadiene to hydrogen in the range of 100 to 0 ˜1 to 100by volume

[0066] With regard to the aforementioned reactant gas, the mixing ratioof butadiene to hydrogen is preferably in the range of 100 to 0˜1 to 25by volume.

[0067] Additionally, the method for manufacturing a magnetic recordingmedium according to the present invention may comprise a method formanufacturing a magnetic recording medium by means of exposing a disc,in which both surfaces of the non-magnetic substrate are layered with anon-magnetic base film and magnetic film, to a reactant gas containingcarbon atoms, while supplying electrical power to electrodes arranged onboth sides of the disc to generate plasma, and form a carbon protectivefilm on both sides of the disc, using the aforementioned reactant gas asa starting material, according to a plasma CVD method; wherein biasapplying is performed to the disc at the time of forming the carbonprotective film; the electrical power supplied to the aforementionedelectrodes comprises high frequency electrical power, and the reactantgas comprises either butadiene gas or a mixed gas of butadiene andhydrogen, with a mixing ratio of butadiene to hydrogen in the range of100 to 0˜1 to 100 by volume.

[0068] When forming the carbon protective film, it is preferable to makethe phases of electrical power supplied to each electrode arranged onboth sides of the disc different from each other. The phase differencein the phase of electrical power supplied to each electrode ispreferably in the range of 90˜270°, and in particular, more preferablycomprises the opposite phase (i.e., 180°)

[0069] The thickness of the carbon protective film is preferably in therange of 30˜100 Å

BRIEF DESCRIPTION OF THE DRAWINGS

[0070]FIG. 1 is a schematic structural view, showing the plasma CVDapparatus, used in an embodiment of the method for manufacturing amagnetic recording medium according to the present invention

[0071]FIG. 2 is a cross-sectional view, showing an embodiment of themagnetic recording medium according to the present invention

[0072]FIG. 3 is a schematic structural view, showing the main portion ofthe magnetic recording medium manufacturing apparatus which employs theplasma CVD apparatus shown in FIG. 1

[0073]FIG. 4 is a cross-sectional view, showing an embodiment of themagnetic recording medium according to the present invention.

[0074]FIG. 5 is a schematic structural view, showing the spatterequipment used in an embodiment of the method for manufacturing amagnetic recording medium according to the present invention.

[0075]FIG. 6 is a schematic structural view, showing the ultraviolet rayirradiation equipment used in an embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention

[0076]FIG. 7 is a schematic structural view, showing the washingapparatus used in an embodiment of the method for manufacturing amagnetic recording medium according to the present invention.

[0077]FIG. 8 is a cross-sectional view, showing an embodiment of themagnetic recording medium according to the present invention.

[0078] FIGS. 9(a) and 9(b) are schematic structural views, showing thetexture-processing equipment used in an embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention: FIG. 9(a) shows a front view and FIG. 9(b) shows a side view

BEST MODES FOR CARRYING OUT THE INVENTION

[0079]FIG. 1 shows the plasma CVD apparatus, which serves as the mainportion of the manufacturing apparatus used in an embodiment of themethod for manufacturing a magnetic recording medium according to thepresent invention This plasma CVD apparatus is used to form a carbonprotective film, and comprises a chamber 10 for storing the disc;electrodes 11 and 11 which are arranged in a manner such that they facethe inner surfaces of both walls of chamber 10; high frequencyelectrical power sources 12 and 12 which supply high frequencyelectrical power to the aforementioned electrodes 11 and 11; anelectrical bias source 13 which can be connected to the disc housedinside of the chamber 10, and a supply source 14 for the reactant gaswhich serves as a starting material of the carbon protective film formedonto the disc

[0080] The chamber 10 is connected to introduction tubes 15 and 15 whichdirect the reactant gas supplied from the supply source 14 into thechamber 10, and an exhaust tube 16 which sends gas inside of the chamber10 out of the system. This exhaust tube 16 is provided with an exhaustvolume regulating valve 17, which allows for the appropriate regulationof the inner pressure of the chamber 10.

[0081] The high frequency electrical power source 12 is preferably onethat can supply an electrical power of 50˜2000 W to the electrode 11,when forming the carbon protective film

[0082] Additionally, preferred examples of the electrical bias source 13may include a high frequency electrical power source and/or a pulse D.C.electrical power source. The high frequency electrical power source canpreferably apply a high frequency electrical power of 10˜300 W to thedisc. Additionally, the pulse D.C. electrical power source canpreferably apply an average voltage of −400˜−10 V to the disc.

[0083] In the following, an embodiment of the method for manufacturing amagnetic recording medium according to the present invention isdescribed, in which the aforementioned manufacturing equipment is usedas an example.

[0084] Initially, a non-magnetic base film and magnetic film are formedon both sides of a non-magnetic substrate according to a method such asa spatter-coating method or the like, to obtain a disc D.

[0085] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, examplesof which may include an aluminium alloy substrate coated with a NiPmetal film, and substrates comprising glass, silicone, and the like Thesurface of the non-magnetic substrate is preferably treated withtexture-processing such as mechanical texture-processing. In particular,the average surface roughness (Ra) is preferably in the range of 1˜20 Å.

[0086] Preferred examples of the material for the non-magnetic base filminclude Cr, alloys of Cr and Ti, alloys of Cr and W, alloys of Cr and V,and alloys of Cr and Si.

[0087] Preferred examples of the material for the magnetic film includeCo alloys such as alloys of Co and Cr, alloys of Co, Cr, and Ta; alloysof Co, Cr, and Pt, alloys of Co, Cr, Pt, and Ta, and the like

[0088] The thicknesses of the non-magnetic base film and magnetic filmare preferably in the range of 50˜1000Å, and 50˜800 Å, respectively

[0089] Subsequently, the disc D is transported into a chamber 10 of theplasma CVD apparatus, and the surface of the disc D is exposed to areactant gas, which is continuously supplied from a supply source 14 viaan introduction tube 15 into the aforementioned chamber 10, where thisgas is removed via an exhaust tube 16 to continuously circulate the gastherein.

[0090] The reactant gas is a mixed gas of hydrocarbon and hydrogen, witha mixing ratio of hydrocarbon to hydrogen in the range of 2 to 1˜1 to100 by volume.

[0091] The hydrocarbon preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons.

[0092] Examples of the lower saturated hydrocarbon may include methane,ethane, propane, butane, octane, and the like. Furthermore, examples ofthe lower unsaturated hydrocarbons may include ethylene, propylene,butylene, butadiene, and the like Additionally, examples of the lowercyclic hydrocarbon may include benzene, toluene, xylene, styrene,naphthalene, cyclohexane, cyclohexadiene, and the like.

[0093] Among the aforementioned hydrocarbons, toluene is particularlypreferred, and the mixing ratio of toluene to hydrogen is preferably inthe range of 1 to 15˜1 to 20 by volume

[0094] Hereinafter, a “lower hydrocarbon” signifies a hydrocarbon having1˜10 carbon atoms. In addition, a “cyclic hydrocarbon” represents ahydrocarbon possessing a ring structure such as a benzene ring, and thelike

[0095] The reason for limiting the mixing ratio of hydrocarbon andhydrogen to the aforementioned range is twofold: a mixing ratio ofhydrocarbon to hydrogen falling below the aforementioned range resultsin a reduced coating rate, which is unsuitable for practical, industrialproduction. On the other hand, a mixing ratio exceeding theaforementioned range, results in a high stress remaining within thecarbon protective film, which in turn lowers the adhesion strength andCSS resistance of the resultant carbon protective film

[0096] In addition, a lower hydrocarbon is preferably used as thehydrocarbon—if the number of carbon atoms of the hydrocarbon exceeds theaforementioned range, it is difficult to supply the hydrocarbon as agas, and in addition, at the time of discharge, difficulty with thedecomposition of hydrocarbons is encountered, which in turn leads to acarbon protective film containing high polymers that are inferior instrength.

[0097] When performing the aforementioned operation, the flow rate ofthe reactant gas is preferably 50˜500 sccm. In addition, the innerpressure of the chamber 10 is preferably set at a predetermined valuesuch as 0.1˜10 Pa, by means of appropriately adjusting the flow rate ofthe exhaust gas from the chamber 10, using the exhaust regulating valve17.

[0098] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a carbonprotective film is formed on both sides of the disc D by means of plasmachemical gas phase growth, using the aforementioned reactant gas as astarting material The thickness of the carbon protective film ispreferably in the range of 30˜100 ÅThe carbon protective film can beformed at the same time on both sides of the disc D.

[0099] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different from each other. By means of making the phases ofelectrical power supplied to each electrode different, the coating rateand durability of the protective film can be improved. The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular the opposite phase (i e,180°) is preferred.

[0100] In addition, when forming the carbon protective film, it ispreferable to form a film while performing bias applying, such as highfrequency bias or pulse D.C bias, to the disc D, using the electricalbias source 13. When using a high frequency electrical source as theelectrical bias source 13, high frequency electrical power of 10˜300 Wis preferably applied to the disc D. Additionally, when using a pulse DC electrical source as the electrical bias source 13, a voltage of−400˜−10 V (at an average) is preferably applied to the disc DFurthermore, the width of pulse is preferably in the range of 10˜50000ns, and the frequency is preferably in the range of 10 kHz˜1 GHz

[0101] When performing bias applying to the disc D, bias applying may beperformed directly to the disc D, or alternatively bias applying may beperformed via a disc carrier (not shown)

[0102] In order to accommodate for practical, industrial production, thecoating rate of the carbon protective film is preferably at least 200Å/min, and more preferably at least 400 Å/min

[0103] In addition, a lubricating film may be provided onto theprotective film, by means of applying lubricant such as a fomblinlubricant, perfluoropolyether, and the like, according to a dippingmethod or the like.

[0104] In the following, the effects of the present invention areexplained in detail using concrete examples

Test Examples 1˜12

[0105] An aluminium substrate coated with a NiP metal film, which hadbeen treated with texture-processing using an alumina slurry to form anaverage surface roughness of 20 Å, was set into the chamber of a DCMagnetron Spatter Apparatus, and the gas within the chamber wasexhausted to an ultimate vacuum level of 2×10⁻⁶ Torr. Subsequently, abase film comprising Cr with a thickness of 400 Å, and a magnetic filmcomprising an alloy of Co₈₂Cr,₁₅Ta₃ (at %) were successively formed onboth sides of the substrate, to obtain a disc D

[0106] Subsequently, the disc D was transported into a chamber 10 of theaforementioned plasma CVD apparatus, and a mixed gas of hydrocarbon andhydrogen comprising a mixing ratio shown in Table 1 was supplied intothe chamber as a reactant gas The inner pressure of the chamber 10 wasmaintained at 2 Pa

[0107] At the same time, high frequency electrical power (of 13.56 MHz)of 300 W was supplied to the electrodes 11 to generate plasma while ahigh frequency bias of 50 W, under the conditions shown in Table 1, wasapplied to the disc D, to form a carbon protective film with a thicknessof 50 Å on both sides of the disc D The temperature of the disc D duringcoating was maintained at 130° C. (In Test Example 9, the electricalpower supplied to the electrode 11 was 600 W, and the temperature of thedisc during coating was 136° C. Furthermore, the bias used in TestExample 3 comprised a D C bias of −200 V) The distance between the discD and electrode 11 was set at 30 mm Furthermore, in the table, the “RFphase difference” signifies the difference in the phase of electricalpower supplied to the two electrodes 11 and 11 TABLE 1 Bias RF Mixingfre- dif- Coating ratio quency ference rate Gas type (sccm) (kHz) (°)(Å/min) Note Test Ex- Toluene 10:150 400 180 335 ample 1 Test Ex-Toluene 10:120 400 0 202 ample 2 Test Ex- Toluene 10:120 D.C 180 188−200 V ample 31 bias Test Ex- Toluene 10:120 400 180 460 ample 4 TestEx- Toluene 15:120 400 180 1098 ample 5 Test Ex- Toluene 100:50  400 1801181 ample 6 Test Ex- Toluene 100:0   400 180 2344 ample 7 Test Ex-Methane 100:0   400 180 324 ample 8 Test Ex- Methane 60:60  no bias 0161 ample 9 Test Ex- Ethane 100:0   400 180 385 ample 10 Test Ex-Acetone 100:0   400 180 221 ample 11 Test Ex- Toluene 10:150 no bias 180290 ample 12

[0108] Table 1 shows the coating rates of each carbon film ComparingTest Examples 4 through 7, it is clear that increasing the mixing ratioof toluene results in an increased coating rate However, in TestExamples 6 and 7, the coating rate did not improve relative to themixing ratio of toluene This result is assumed secondary to thediffusion of plasma from sparks incurred during discharge In addition,when comparing Test Examples 1-5 and 12, it is clear that theimprovements in the coating rate can be achieved by means of biasapplying, in particular the high frequency bias applying, and/or makingthe phases of the electrical power supplied to electrodes which are atfront and reverse sides of the disc different from each other

[0109] Subsequently, a fomblin lubricant was applied to the carbonprotective film at 15 Å, to obtain a magnetic recording medium

[0110] The resultant magnetic recording medium was used in the CSS test,as described in the following In this test, a CSS operation wasperformed 20000 times using an MR head, wherein once cycle consisted ofbuilding up for five seconds, high speed rotation for one second;trailing down for five seconds; and parking for one second, at arotational speed of 7200 rpm, under the conditions of ambienttemperature and normal humidity.

[0111] Furthermore, with regard to Test Examples 3˜5, a stiction valuewas monitored, and another CSS test was performed in which a CSSoperation was carried out 5000 times, using the same cycle as describedabove, at a temperature of 40° C. with a humidity of 80% The results areshown in Table 2. When a crash occurred during the CSS test performedunder a normal temperature and pressure, the number of CSS cycles at thetime when the crash occurred was recorded.

[0112] In Table 2, the ratio of the g-band peak value (vG-line) andd-band peak value (Id/Ig) according to Raman spectral analysis (argonion laser excitation) is also shown for reference In general, when acarbon film is analyzed according to the Raman spectral analysis, aprofile with two peaks is obtained in which a g-band is measured atapproximately 1530 cm⁻¹ and a d-band is measured at approximately 1400cm⁻¹ A smaller value for Id/Ig, or alternatively, a higher frequency forthe g-band peak results in greater diamond-like characteristics in thecarbon film.

[0113] Subsequently, the same magnetic recording medium used in the CSStest was used in a corrosion test, as described in the following. Thistest comprised the steps of leaving the test medium in an oven at atemperature of 60° C. with a humidity of 80% for 96 hours, subsequentlysoaking the medium in 50 cc of pure water for 30 minutes; and measuringthe amount of Co extracted in the pure water In addition, another test,was performed in the same manner as described above, with the exceptionthat the aforementioned magnetic recording medium was allowed to sit ata normal temperature (25° C.) and humidity (50%) for 96 hours Theresults are shown in Table 2

[0114] Furthermore, in the present specification, the term “crash”signifies the occurrence of a head crash during the CSS test, while thephrase “no crash” signifies that such a head crash did not occur TABLE 2CSS Test Co Corrosion Test Raman Normal 60° C. Analysis temp. & 40° C.Normal 80% νG-line pressure 80% Stiction (μg/disc) (μg/disc) (cm⁻¹)Id/Ig Test Example 1 8500 — — 0.07 0.17 1543.2 0.56 Test Example 2 5000— — 0.08 0.18 1550.2 0.66 Test Example 3 No crash 5000 0.44 0.06 0.141559.2 1.56 Test Example 4 No crash 5000 0.38 0.05 0.07 1553.0 0.63 TestExample 5 No crash 5000 0.34 0.08 0.12 1524.5 0.39 Test Example 6 7000 —— 0.18 0.28 1547.2 0.78 Test Example 7  250 — — 0.22 0.54 — — TestExample 8  10 — — 0.11 0.18 — — Test Example 9 4000 — — 0.09 0.19 1534.00.45 Test Example 10  10 — — 0.14 0.22 — — Test Example 11  10 — — 0.130.77 — — Test Example 12  20 — — 0.18 0.25 — —

[0115] From Table 2, it is clear that with the magnetic recording mediummanufactured according to Test Examples 1 through 6, the above describedcrashes did not occur, even when the CSS operation was performed greaterthan 5000 times In particular, Test Examples 3˜5, did not result incrashes even when the CSS operation was performed 20000 times, and alsodid not result in crashes when the CSS operation was performed 5000times, under the conditions of a temperature of 40° C. and a humidity of80%, airs thus these examples exhibited a favorable performance withregard to resistance to CSS

[0116] On the other hand, Test Example 7, in which the mixing ratio oftoluene and H₂ was out of the range defined in the present invention,and Test Example 12, in which bias applying was not performed, resultedin a modest coating rate, but a magnetic ) medium of inferior durability

[0117] Additionally, the magnetic recording medium obtained accordingTest Examples 8˜11, in which methane, ethane, or acetone was employed,all exhibited an inferior durability.

[0118] In addition, the results of the corrosion test confirmed that theextraction amount of Co of all magnetic recording media wasapproximately 1˜2 ng per medium, leaving no problems with respect topractical use

[0119] Furthermore, the results of the CSS test showed clearly that itis possible to improve the durability of the resultant magneticrecording medium, by means of making the phases of electrical powersupplied to the electrodes on each side of the disc different

[0120] In addition, according to the results of Test Examples 1˜6, it ispossible to form a carbon protective film at a coating rate suitable forindustrial production, and to provide a magnetic recording mediaexhibiting superior performance with respect to their resistance to CSSand resistance to corrosion.

[0121] As described in the aforementioned, according to the presentinvention, it is possible to efficiently form a carbon protective filmpossessing a superior durability Accordingly, it is possible to make thecarbon protective film thinner while maintaining a sufficientdurability, thereby reducing the spacing loss

[0122] Thus, it is possible to efficiently provide a reliable, magneticrecording medium, which can support a sufficiently high recordingdensity without reduction in its output properties.

[0123] In the following, another embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention is described, using an example in which the plasma CVDapparatus shown in FIG. 1 is employed

[0124] Initially, a non-magnetic base film and magnetic film are formedon both sides of the non-magnetic substrate according to a method suchas a spatter-coating method or the like, to obtain a disc D.

[0125] The non-magnetic substrate can comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, asdescribed in the aforementioned the material and thickness of thenon-magnetic base film and magnetic film are also as describedaforementioned

[0126] Subsequently, the disc D, layered with a non-magnetic base filmand magnetic film on the non-magnetic substrate according to theaforementioned operations, is transported into chamber 10 of theaforementioned plasma CVD apparatus, and the surface of the disc D isexposed to the reactant gas, which is continuously supplied from asupply source 14 via an introduction tube 15 into the chamber 10, wherethe gas is exhausted via an exhaust tube 16 to circulate the gas therein

[0127] The reactant gas is preferably a mixed gas comprising hydrocarbonand hydrogen, with a mixing ratio of hydrocarbon to hydrogen in therange of 2 to 1˜1 to 100 by volume, as described in the aforementionedThe hydrocarbon preferably comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons.

[0128] When carrying out this operation, the flow rate of the reactantgas is preferably 50 ˜500 sccm Additionally, the inner pressure of thechamber 10 is preferably set at a predetermined value, such as 0 1˜10 Pa

[0129] At the same time, using the high frequency electrical powersource 12, a high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a carbonprotective film is formed on both sides of the disc D by means of theplasma chemical gas phase growth, using the aforementioned reactant gasas a starting material The thickness of the carbon protective film ispreferably in the range of 30˜100 Å.

[0130] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode different, the coating rate anddurability of the protective film can be improved The difference in thephase of electrical power supplied to each electrode is preferably inthe range of 90˜270°, with a particular preference for the oppositephase (i.e, 180°).

[0131] According to this embodiment of the method for manufacturing amagnetic recording medium, when forming a carbon protective film, it ispreferable to form film while applying pulse D C bias having a frequencyof 1 kHz˜100 GHz (with a cycle of 10 ns˜1 ms) and pulse width of1ns˜500μs, to the disc D, using an electrical bias source 13

[0132] A pulse D.C. bias frequency of less than 1 kHz or exceeding 100GHz, results in a carbon protective film of inferior durability. Inparticular, when the frequency is less than 1 kHz, the coating ratetends to be lower, leading to an unfavorable reduction in the productionefficiency.

[0133] The frequency and pulse width of the aforementioned pulse D Cbias is preferably 10 kHz˜1 GHz, and 10 ns˜50μs, respectively.

[0134] Furthermore, the average voltage of the pulse D.C bias applied tothe disc is preferably −400˜−10 V.

[0135] When the average voltage is less than −400 V, sparks are likelyto be generated during the coating, leading to a high likelihood ofgenerating abnormal growth portions on the surface of the carbonprotective film. When the average voltage exceeds −10 V, the carbonprotective film tends to contain a greater number of high polymers,which are inferior in strength

[0136] In addition, a lubricating film may be provided on the protectivefilm by means of applying the aforementioned lubricant

[0137] Examples of the magnetic recording medium manufactured accordingto the aforementioned manufacturing method may include a magneticrecording medium with the structure shown in FIG. 2

[0138] In the magnetic recording medium according to this embodiment, anon-magnetic substrate S, a non-magnetic base film 31, a magnetic film32, a carbon protective film 33, and a lubricating film 34 are provided

[0139] According to the aforementioned manufacturing method, at the timeof forming the carbon protective film, it is possible to efficientlyform a carbon protective film displaying a superior durability, sincepulse D.C bias with a frequency of 1 kHz˜100 GHz and pulse width of 1ns˜500 μs is applied to the disc Accordingly, it is possible to make thecarbon protective film thinner while also maintaining durability, andthus provide a magnetic recording medium that is capable of reducingspacing loss In addition, it is possible to increase the coating rate,and production efficiency therein

[0140] Therefore, it is possible to efficiently provide a reliable,magnetic recording medium, which can support a sufficiently highrecording density without lowering the output properties thereof

[0141] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 13˜26

[0142] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film (with a thickness of 600 Å) comprising a Cralloy, and a magnetic film comprising a Co alloy were successivelyformed on both sides of the substrate, using spattering device (3010manufactured by Anelva) to obtain a disc D

[0143] Subsequently, the disc D was transported into a chamber 10 of theaforementioned plasma CVD apparatus, and a mixed gas was supplied fromthe supply source 14 into the chamber to achieve a flow rate of 130 sccm

[0144] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 12 by volume, was used as the reactant gasAdditionally, the inner pressure of the chamber 10 was maintained at 6Pa

[0145] At the same time, pulse D.C bias was applied to the disc underthe conditions shown in Table 3, using an electrical bias source 13, andhigh frequency electrical power of 300 W, or alternatively 500 W, wassupplied to the electrodes 11 to generate plasma and form a carbonprotective film with a thickness of 50 Å on both sides of the disc D

[0146] The temperature of the disc D during coating was maintained at130° C. The difference in the phase of high frequency electrical powersupplied to each electrode 11 was set at 180° In addition, the distancebetween the disc D and electrode 11 was set at 30 mm

[0147] Subsequently, a magnetic recording medium was obtained by meansof applying a fomblin lubricant (Fomblin Zdol 2000) to the carbonprotective film, according to a dipping method, to form a lubricatingfilm thereon with a thickness of 20 Å

[0148] The CSS test described in the following was performed on theresultant recording media In the test, using a MR head, a CSS operationwas performed on the magnetic recording medium 10,000 times, at arotational speed of 7200 rpm, and a temperature of 40° C. with ahumidity of 80% After allowing the magnetic recording medium to sit for1 hour, the dynamic stiction value was monitored The results are shownin Table 3.

[0149] In the table, the term “plasma RF electrical power” representsthe electrical power supplied to the electrodes 11 during the formationof the carbon protective film. TABLE 3 Plasma Coat- Bias RF ing volt-electrical rate Stic- Bias Pulse age power (Å/ tion frequency width (V)(W) min) (−) Test Ex- 1 kHz 500 ns −120 500 405 0.81 ample 13 Test Ex-200 kHz 500 ns −120 500 753 0.40 ample 14 Test Ex- 2 MHz 250 ns −120 300712 0.55 ample 15 Test Ex- 10 MHz 50 ns −120 500 844 0.46 ample 16 TestEx- 200 kHz 1 ns −120 500 477 0.88 ample 17 Test Ex- 200 kHz 1000 ns−120 500 777 0.44 ample 18 Test Ex- 1 kHz 500000 ns −120 500 624 0.67ample 19 Test Ex- 70 GHz 50 ns −100 500 553 0.66 ample 20 Test Ex- 101GHz 1 ns −100 500 413 Crash ample 21 Test Ex- 0.5 kHz 500 ns −100 500388 Crash ample 22 Test Ex- 200 kHz 500 ns −400 500 1042 Crash ample 23Test Ex- 200 kHz 0.5 ns −100 500 340 Crash ample 24 Test Ex- 1 kHz 0.8ms −100 500 314 Crash ample 25 Test Ex- — — — 300 335 Crash ample 26

[0150] From the results of the CSS test shown in Table 3, it is clearthat the magnetic recording media obtained according to the method forapplying pulse D.C bias with a frequency of 1 kHz˜100 GHz and pulsewidth of 1 ns˜500 μs to the disc, at the title ot forming the carbonprotective film, were superior in durability and exhibited a highercoating rate

[0151] As described in the aforementioned, according to the presentinvention, it is possible to efficiently form a carbon protective filmwith a superior durability Accordingly, it is possible to make thecarbon protective film thinner while also maintaining a sufficientdurability, and thereby reduce spacing loss

[0152] Therefore, it is possible to provide a highly reliable, magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties

[0153]FIG. 3 shows the manufacturing equipment used in anotherembodiment of the method for manufacturing a magnetic recording mediumaccording to the present invention. The manufacturing equipment shownherein is provided with a spattering device 1, temperature regulatingdevice 2, and plasma CVD apparatus 3.

[0154] The spattering device 1 is used to form a non-magnetic base film,magnetic film, and the like, on a non-magnetic substrate, and maycomprise any apparatus generally used for manufacturing a magneticrecording medium

[0155] The temperature regulating device 2 sets the temperature of thedisc sent to the aforementioned plasma CVD apparatus 3 to apredetermined degree, and comprises a chamber 4, which stores the disc,and a supply source for supplying the temperature adjusting gas 5, whichis used for adjusting the temperature of the disc in the chamber 4 Theaforementioned chamber 4 is connected to an introduction tube 7, whichdirects the temperature adjusting gas supplied from the supply source 5into the chamber 4, and an exhaust tube 8, which expels the gas insidethe chamber 4 out of the system

[0156] The aforementioned chamber 4 comprises an airtight structure, andis provided with a transport entrance 4 a, which transports a discpassing through the spattering device 1 into the chamber 4, and atransport exit 4 b, which transports the disc out of the chamber 4towards the aforementioned plasma CVD apparatus 3

[0157] The aforementioned plasma CVD apparatus 3 may comprise the samestructure shown in FIG. 1

[0158] In the following, another embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention is described, using an example in which the aforementionedmanufacturing equipment is employed

[0159] Initially, using a spattering device 1, a non-magnetic base filmand magnetic film are formed on both sides of the non-magneticsubstrate, to obtain a disc D

[0160] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, asdescribed in the aforementioned. The material and thickness of thenon-magnetic base film and magnetic film are similarly as described inthe aforementioned

[0161] In general, when forming the non-magnetic base film and magneticfilm, the temperature of the non-magnetic substrate is approximately250˜350° C.

[0162] Subsequently, the disc D, layered with the non-magnetic base filmand magnetic film on the non-magnetic substrate according to theaforementioned operations, is transported into the chamber 4 of thetemperature regulating device 2 through the transport entrance 4 a, andthe disc D in the chamber 4 is exposed to the temperature adjusting gas,which is supplied from the supply source 5 via the introduction tube 7into the chamber 4, from which the gas is exhausted via the exhaust tube8 to circulate the gas within

[0163] The temperature adjusting gas is not particularly limited, aslong as it does not adversely affect the disc D; examples of theaforementioned gas may include hydrogen, nitrogen, helium, neon, argon,and the like.

[0164] The temperature of the temperature adjusting gas is appropriatelydetermined according to the desired temperature of the disc D, and otherconditions, such as a flow rate of the temperature adjusting gas and thelike; however, this temperature is preferably in the range of 0˜250° C.

[0165] When carrying out this operation, the flow rate of thetemperature adjusting gas is preferably 50˜1500 sccm Additionally, theinner pressure of the chamber 4 is preferably set at a predeterminedvalue, e.g., 1˜30 Pa by means of appropriately adjusting the flow rateof the exhaust gas from the chamber 4

[0166] By means of exposing the disc D to the temperature adjusting gas,heat exchange is performed between the disc D and temperature adjustinggas This operation is continued until the temperature of the disc D isin the range of 100˜250° C., preferably 150˜250° C., and more preferably150˜200° C.

[0167] If the temperature of the disc D is less than 100° C., thedensity of the carbon protective film formed onto the disc D, accordingto the operation described in the following, results in a low value,which leads to an inferior durability

[0168] If the temperature exceeds 250° C., the kinetic energy of themolecules of the reactant gas becomes too high during the formation ofthe carbon protective film according to the operation described in thefollowing, which in turn results in difficulty in adhering the moleculesto the disc D, thereby leading to a low coating rate In addition, theresultant carbon protective film contains a greater number of highpolymer components that are inferior in strength, which then lead to aninferior durability.

[0169] Subsequently, the disc D is transported out of the temperatureregulating device 2 via the transport exit 4 b, and immediately intochamber 10 of the aforementioned plasma CVD apparatus 3, where thesurface of the disc D, the temperature of which has been adjusted to theaforementioned value by means of the temperature regulating device 2, isexposed to a reactant gas, which is supplied from the supply source 14via the introduction tube 15 into the chamber 10. Gas is continuouslyexhausted through the exhaust tube 16 to circulate the gas withinchamber 10.

[0170] The reactant gas is preferably a mixed gas of hydrocarbon andhydrogen with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume as described in the aforementioned, and thehydrocarbon preferably comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons.

[0171] When carrying out the operation, the flow rate of the reactantgas is preferably in the range of 50˜500 sccm. In addition, the innerpressure of the chamber 10 is preferably set at a predetermined value,e.g., 0 1˜10 Pa by means of appropriately adjusting the flow rate of theexhaust gas from the chamber 10, using the exhaust regulating valve 17

[0172] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma and form the carbonprotective film on both sides of the disc D by means of plasma chemicalgas phase growth, using the aforementioned reactant gas as a startingmaterial. The thickness of the carbon protective film is preferably inthe range of 30˜100 Å

[0173] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode different By means of making the phases of electrical powersupplied to each electrode 11 different, it is possible to improve thecoating rate and durability of the protective film The difference in thephase of electrical power supplied to each electrode is preferably inthe range of 90 ˜270°, and in particular, more preferably comprises theopposite phase (i e, 180°)

[0174] Herein, it is preferable to form the film while performing biasapplying such as high frequency bias and pulse D.C. bias to the disc,using the electrical bias source 13.

[0175] The conditions of bias, such as voltage and the like, arepreferably as described in the aforementioned.

[0176] In addition, a lubricating film may be provided on the protectivefilm by means of applying a lubricant such as fomblin lubricant,perfluoropolyether, and the like, according to a dipping method or thelike.

[0177] In the aforementioned manufacturing method, since the disctemperature is set at 100˜250° C. in advance, during formation of thecarbon protective film, the carbon protective film is able to support ahigher density, which leads to a superior durability. Accordingly, it ispossible to make the carbon protective film thinner, while alsomaintaining a sufficient durability, and thus provide a magneticrecording medium that is capable of reducing spacing loss at the time ofrecording and replay

[0178] Therefore, it is possible to provide a highly reliable, magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof

[0179] In addition, it is possible to accelerate adhesion of thematerials of the carbon protective film, derived from the reactant gas,to the disc D, and thereby increase the coating rate and productionefficiency.

[0180] The reason for the improvement in durability of the carbonprotective film by means of setting the temperature of the disc D in theaforementioned range at the time of forming the aforementioned carbonprotective film is unclear, however, the following is hypothesized

[0181] Namely, if the temperature is less than the aforementioned range,the kinetic energy of the molecules of the materials of the carbonprotective film at the time of forming the carbon protective film islow, which results in an insufficient tightness and irregularconfiguration of the carbon protective film molecules Accordingly, theresultant carbon protective film comprises a lower density, leading toan inferior durability of the carbon protective film

[0182] In addition, if the temperature exceeds the aforementioned range,high polymer reactions such as polymerization, condensation, and thelike are more likely to occur, and the carbon compounds, derived fromthe supplied reactant gas, will tend to form high polymers on thesurface of the disc D. As a result, the number of high polymercomponents in the carbon protective film, which exhibit an inferiorstrength, increases, thereby leading to an inferior durability in thecarbon protective film.

[0183] In the following the effects of the present invention arespecified, using concrete examples.

Test Examples 27˜32

[0184] Magnetic recording medium was manufactured as described in thefollowing, using the equipment shown in FIGS. 1 and 3.

[0185] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film (with a thickness of 600 Å) comprising a Cralloy, and a magnetic film comprising a Co alloy were successivelyformed on both sides of the substrate, using a spattering device (3010manufactured by Anelva), to obtain a disc D At the time of forming theaforementioned non-magnetic base film and magnetic film, the temperatureof the substrate was set at 250° C.

[0186] Subsequently, the disc D was transported into the chamber 4 ofthe temperature regulating device 2, where hydrogen gas (the temperatureof which was adjusted in advance to 20° C.) for use in adjusting thetemperature of the disc was supplied at a flow rate shown in Table 4 Inthis manner, the temperature of the disc D was adjusted to the valuesshown in Table 4 by means of exposing the disc D to the hydrogen gas fora period of time shown in Table 4 Furthermore, the temperature of thedisc D was measured by means of a radiation thermometer provided inchamber 4 The inner pressure of the chamber 4 was set at 10 Pa

[0187] Subsequently, the disc D was immediately transported into thechamber 10 of the plasma CVD apparatus 3, and a reactant gas wassupplied from the supply source 14 into the chamber 10 at a flow rate of130 sccm A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 10 by volume, was used as the reactant gasIn addition, the inner pressure of the chamber 10 was set at 6 Pa

[0188] At the same time, high frequency electrical power of 500 W wassupplied to the electrodes 11 to generate plasma and form a carbonprotective film with a thickness of 50 Å on both sides of the disc D.The temperature of the disc D was set as shown in Table 4, by means ofthe aforementioned temperature regulating device 2. In addition, highfrequency electrical power of 50W was applied to the disc D, using theelectrical bias source 13. In addition, the difference in the phase ofhigh frequency electrical power supplied to each electrode 11 was set at180°

[0189] Subsequently, fomblin lubricant was applied to the carbonprotective film, to form a lubricating film with a thickness of 15 Å,and yielding a magnetic recording medium.

[0190] The CSS test described in the following was performed on theresultant magnetic recording media In the CSS test, using MR head, a CSSoperation was performed 20,000 times at a rotational speed of 7200 rpm,and a temperature of 40° C. with a humidity of 80% The dynamic stictionvalue was monitored after allowing the magnetic recording medium to sitfor one hour. The results are shown in Table 4

Test Examples 33˜36

[0191] The magnetic recording medium was manufactured in the same manneras in the aforementioned test examples, with the exception that thetemperature of the disc D, at the time of forming the carbon protectivefilm, was adjusted by means of changing the temperature of the disc D atthe time of transport into the temperature regulating device 2, and/orthe flow rate or temperature of the temperature adjusting gas in thetemperature adjusting operation, using the temperature regulating device2 The test results are also shown in Table 4 TABLE 4 Flow rate Disctemp. Coating Temp of temp. when rate regulating adjusting forming (Å/Stiction time (sec) gas (sccm) film (° C.) min) (−) Test Example 27 8 80238 617 0.72 Test Example 28 13 80 220 660 0.66 Test Example 29 20 80174 765 0.67 Test Example 30 8 200 191 720 0.63 Test Example 31 13 200150 830 0.73 Test Example 32 6 80 250 506 0.68 Test Example 33 0 0 327339 2.59 Test Example 34 2 80 304 381 1.48 Test Example 35 13 2000 501850 Crash Test Example 36 0 0 400 225 Crash

[0192] From the results shown in Table 4, it is clear that the magneticrecording media manufactured according to a method in which thetemperature of the disc D was set in the range of 100˜250° C., at thetime of forming the carbon protective film, exhibited a lower stictionvalue after performing the CSS test and a superior durability, inaddition to a higher coating rate, when compared to the magneticrecording media manufactured according to a method in which thetemperature of the disc D was set outside of the aforementioned range

[0193] As described in the aforementioned, in the method formanufacturing a magnetic recording medium according to the presentinvention, it is possible to provide a carbon protective film comprisinga high density and superior durability Accordingly, it is possible tomanufacture a thinner carbon protective film while also maintaining asufficient durability, and thus to provide a magnetic recording mediumthat is capable of reducing spacing loss at the time of recording andreplay

[0194] Therefore, it is possible to provide a highly reliable magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof Additionally, itis possible to also increase the production efficiency

[0195] In the following, another embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention is described, using an example which employs theaforementioned plasma CVD apparatus shown in FIG. 1.

[0196] Initially, a non-magnetic base film and magnetic film were formedon both sides of non-magnetic substrate, according to a method such as aspatter-coating method, and the like, to obtain a disc D.

[0197] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, asdescribed in the aforementioned. The material and thickness of thenon-magnetic base film and magnetic film are also as described in theaforementioned.

[0198] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to the reactant gas, which is supplied from the supply source14 via the introduction tube 15 into the chamber 10, from which the gasis exhausted through the exhaust tube 16 to circulate the gas within

[0199] The reactant gas comprises a mixed gas of hydrocarbon andhydrogen, with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume The hydrocarbon preferably comprises at leastone type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons.

[0200] When carrying out this operation, the flow rate of the reactantgas is preferably in the range of 50˜500 sccm.

[0201] According to the method of this embodiment, the flow rate of theexhaust gas from the chamber 10 is appropriately adjusted, using theexhaust regulating valve 17 provided in the exhaust tube 16, such thatthe pressure of the reactant gas in the chamber 10 falls into the rangeof 0.1˜10 Pa, preferably 2˜6 Pa, and more preferably 4 5˜6 Pa

[0202] The reason for setting the pressure in the aforementioned rangeis that the coating rate decreases if the pressure is less than 0 1 Pa,while the durability of the carbon protective film deteriorates if thepressure exceeds 10 Pa

[0203] At the same time, high frequency electrical power of preferably50˜2000 W is supplied to the electrodes 11, using a high frequencyelectrical power source 12, to generate plasma, and thereby form acarbon protective film formed on both sides of the disc D by means ofthe plasma chemical gas phase growth, using the aforementioned reactantgas as a starting material. The thickness of the carbon protective filmis preferably in the range of 30˜100 Å.

[0204] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different By means of shifting the phase of electricalpower supplied to each electrode, the coating rate and durability of theprotective film can be improved. The difference in the phase ofelectrical power supplied to each electrode is preferably in the rangeof 90˜270°, and in particular the opposite phase (i.e., 180°) ispreferred

[0205] In addition, when forming the carbon protective film, it ispreferable to form the film while performing bias applying, such as highfrequency bias or pulse D C bias, to the disc D, using an electricalbias source 13

[0206] The preferred conditions of bias, e g., voltage and the like areas described in the aforementioned

[0207] In addition, a lubricating film may be provided on the protectivefilm by means of applying the aforementioned lubricant

[0208] In the aforementioned manufacturing method, since the pressure ofthe reactant gas is maintained at 0.1˜10 Pa, at the time of forming thecarbon protective film, the resultant carbon protective film exhibits asuperior durability Accordingly, it is possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thus provide a magnetic recording medium that is capable of reducingspacing loss at the time of recording and replay.

[0209] Thus, it is possible to provide a highly reliable magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof

[0210] In addition, it is possible to increase the coating rate andproduction efficiency

[0211] The reason that a carbon protective film with superior durabilitycan be efficiently formed by means of setting the pressure of thereactant gas in the aforementioned range at the time of forming theaforementioned carbon protective film is hypothesized in the following.

[0212] Setting the pressure for the reactant gas in the aforementionedrange results in the excitation and activation of a portion of thehydrocarbons in the reactant gas by the plasma. After decomposition ofthe potion of the hydrocarbons, this portion of hydrocarbons arerestructured onto disc D to form a diamond-like carbon (referred tohereinafter as “DLC”) with high hardness. Thus, the resultant carbonprotective film exhibits superior strength.

[0213] In addition, a sufficient reactant gas is thus supplied to thechamber 10, leading to a high coating rate.

[0214] On the other hand, if the pressure of the reactant gas is lessthan the aforementioned range, the number of hydrocarbon molecules inthe reactant gas which exist in the chamber 10 becomes insufficient,leading to an inadequate coating rate

[0215] In addition, if the pressure exceeds the aforementioned range,the number of hydrocarbon molecules in the reactant gas present withinchamber 10 becomes too high, which in turn leads to difficulty indecomposing the hydrocarbons even in the presence of the plasma. As aresult, a portion of the hydrocarbons in the reactant gas remain adheredto the disc D without undergoing decomposition, and the overall contentof DLC in the resultant carbon protective film decreases, leading to acarbon protective film with an inferior strength

[0216] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 37˜43

[0217] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0 8 mm) was treated withmechanical texture-processing to form an average surface roughness of 23Å, a non-magnetic base film (with a thickness of 600 Å) comprising a Cralloy, and a magnetic film comprising a Co alloy were successivelyformed on both sides of the substrate, using a spattering device (3010manufactured by Anelva), to obtain a disc D

[0218] Subsequently, the disc D was transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and a mixed gas was suppliedfrom the supply source 14 into the chamber to achieve a flow rate of 130sccm. A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 10 by volume, was used as the reactant gas.

[0219] The inner pressure of the chamber 10 at this time was maintainedas shown in Table 5, by means of adjusting the exhaust regulating valve17

[0220] At the same time, high frequency electrical power of 500 W wassupplied to the electrodes 11 to generate plasma, and thereby form acarbon protective film with a thickness of 50Å on both sides of the discD In addition, high frequency electrical power of 50 W was applied tothe disc D, using the electrical bias source 13 In addition, thedifference in the phase of high frequency electrical power supplied toeach electrode 11 was set at 180°.

[0221] Subsequently, fomblin lubricant was applied to the carbonprotective film, to form a lubricating film with a thickness of 15 Å,thereby yielding a magnetic recording medium.

[0222] The CSS test described in the following was performed on themagnetic recording media In the CSS test, using an MR head, a CSSoperation was performed 20,000 times at a rotational speed of 7200 rpm,and a temperature of 40° C. with a humidity of 80%. The dynamic stictionvalue was monitored after allowing the magnetic recording medium to sitfor one hour The results are shown in Table 5

[0223] Additionally, Raman spectral analysis (argon ion laserexcitation) was performed on the aforementioned magnetic recordingmedia, using a Raman spectral analysis apparatus (manufactured by JEOLCo , Inc) These results are also shown in Table 5.

[0224] In general, when a carbon film is analyzed according to the Ramanspectral analysis, a profile with two peaks is obtained in which ag-band is measured at approximately 1530 cm⁻¹ and a d-band is measuredat approximately 1400 cm⁻¹ A smaller value for Id/Ig, or alternatively,a higher frequency for the g-band peak results in greater diamond-likecharacteristics in the carbon film

Test Examples 44 and 45

[0225] A magnetic recording medium was manufactured in the same manneras the aforementioned test example, with the exception that the pressureof the reactant gas in the chamber 10 was modified by means of adjustingthe exhaust regulating valve 17 The test results are shown in Table 5

[0226] Additionally, Raman spectral analysis was performed on thesemagnetic recording media. The results also displayed in Table 5. TABLE 5Pressure Results of Raman of reactant spectral analysis gas (Pa)Stiction (−) G-line (cm⁻¹⁾ Id/Ig (−) Test Example 37 2.30 0.71 1540.90.62 Test Example 38 3.60 0.50 1539.9 0.56 Test Example 39 4.70 0.431553.0 0.63 Test Example 40 5.30 0.49 1545.2 0.53 Test Example 41 5.800.46 1547.5 0.66 Test Example 42 6.40 0.83 1535.6 0.51 Test Example 430.88 0.77 1558.9 0.76 Test Example 44 13.1 1.24 1565.5 3.77 Test Example45 164 Crash 1566.0 3.89

[0227] From the results shown in Table 5, it is clear that the magneticrecording media, manufactured according to a method in which thepressure of the reactant gas at the time of forming the carbonprotective film is maintained at 0 1˜1.0 Pa, are superior in durabilitywhen compared to magnetic recording media manufactured according to amethod wherein the pressure is set outside of the aforementioned range

[0228] Moreover, among the aforementioned, it is clear that magneticrecording media manufactured according to a method in which the pressureof the reactant gas is maintained at 2˜6 Pa, in particular, exhibit asuperior durability

[0229] In addition, the carbon protective films of magnetic recordingmedia, manufactured according to a method wherein the pressure of thereactant gas is maintained in the aforementioned range, display g-bandpeak values at higher frequency when compared to those manufacturedaccording to a method wherein the pressure is set outside of theaforementioned range, which in turn lead to a low Id/Ig and greater DLCcontent

[0230] As described in the aforementioned, in the method formanufacturing a magnetic recording medium according to the presentinvention, a carbon protective film exhibiting a superior durability isproduced by means of maintaining the pressure of the reactant gas at 01˜10 Pa at the time of forming the carbon film Accordingly, it ispossible to make the carbon protective film thinner while alsomaintaining a sufficient durability, and thus to provide a magneticrecording medium that, is capable of reducing spacing loss at the timeof recording and replay.

[0231] Therefore, it is possible to provide a highly reliable magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof

[0232] In addition, it is also possible to increase the coating rate,and production efficiency.

[0233] In the following, another embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention, using an example in which the aforementioned plasma CVDapparatus shown in FIG. 1 is employed.

[0234] Initially, a non-magnetic base film and magnetic film were formedon both sides of a non-magnetic substrate, according to a method such asa spatter-coating method or the like, to obtain a disc D

[0235] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, asdescribed in the aforementioned. The material and thickness of thenon-magnetic base film and magnetic film are also as described in theaforementioned.

[0236] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to the reactant gas, which is supplied from the supply source14 through the introduction tube 15 into the chamber 10. The gas is thenexhausted from chamber 10 via the exhaust tube 16 to circulate the gastherein

[0237] According to the manufacturing method of this embodiment, thereactant gas is that comprises a mixed gas of hydrocarbon and hydrogen,with a mixing ratio of hydrocarbon to hydrogen in the range of 2 to 1˜1to 100 by volume, into which nitrogen gas is added at a adding volume of0 1˜100% of the mixed gas, and preferably 50˜100 vol %

[0238] The hydrocarbon preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons,

[0239] The nitrogen gas is added into the aforementioned mixed gas at aadding volume of 0.1˜100% of the mixed gas. A adding volume of thenitrogen gas to the mixed gas of less than 0.1% by volume, oralternatively exceeding 100% by volume reduces the hardness of thecarbon protective film, which in turn leads to an insufficientdurability.

[0240] In addition, the reason that the mixing ratio of theaforementioned mixed gas of hydrocarbon to hydrogen is preferably in theaforementioned range since a mixing ratio of the hydrocarbon to hydrogenin the mixed gas of less than the aforementioned range leads to areduced coating rate which is unsuitable for practical, industrialproduction Similarly, a mixing ratio exceeding the aforementioned rangeresults in an increase in the stress remaining within the carbonprotective film, leading to inferior adhesion and an inferior resistanceto CSS in the resultant carbon protective film

[0241] In addition, a lower hydrocarbon is preferably used as thehydrocarbon if the number of carbon atoms of the hydrocarbon exceeds theaforementioned range, it is difficult to supply the hydrocarbon as agas, and in addition, at the time of discharge, difficulty with thedecomposition of hydrocarbons is encountered, which in turn leads to acarbon protective film containing high polymers that are inferior instrength.

[0242] When carrying out the operation, the flow rate of the reactantgas is preferably in the range of 50˜500 sccm In addition, the innerpressure of the chamber 10 is preferably set at the predetermined value,e.g., 0.1˜10 Pa.

[0243] At the same time, high frequency electrical power of preferably50˜2000 W is supplied to the electrodes 11, using the high frequencyelectrical power source 12, to generate plasma, and thereby form acarbon protective film on both sides of the disc D by means of plasmachemical gas phase growth, using the aforementioned reactant gas as astarting material. The thickness of the carbon protective film ispreferably in the range of 30˜100 Å

[0244] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different By means of shifting the phase of electricalpower supplied to each electrode, it is possible to improve both thecoating rate and durability of the protective film. The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular the opposite phase (i.e.,180°) is preferred.

[0245] In addition, when forming the carbon protective film, it ispreferable to form the film while performing bias applying, such as highfrequency bias or pulse D.C. bias, to the disc D, using the electricalbias source 13.

[0246] The conditions of bias such as voltage and the like arepreferably as described in the aforementioned.

[0247] In addition, a lubricating film may be provided on the protectivefilm by means of applying the aforementioned lubricant

[0248] In the aforementioned manufacturing method, as the reactant gas,by means of adding a nitrogen gas, at a adding volume of 0 1˜100% of themixed gas, and preferably 50˜100% by volume, into the mixed gascomprising hydrocarbon and hydrogen, with a mixing ratio of hydrocarbonto hydrogen in the range of 2 to 1˜1 to 100 by volume, at the time offorming the carbon protective film, the carbon protective film exhibitsa superior durability Accordingly, it is possible to make the carbonprotective film thinner while maintaining a sufficient durability, andthus provide a magnetic recording medium that is capable of reducingspacing loss at the time of recording and replay

[0249] Therefore, it is possible to provide a highly reliable magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof

[0250] The reason that it is possible to form a carbon protective filmpossessing a superior durability by means of using a mixed gas, in whichthe nitrogen gas has been added at a adding volume of 0.1˜100% of themixed gas as the reactant gas at the time of forming the aforementionedcarbon protective film, is unclear, but is hypothesized as follows

[0251] It is hypothesized that by means of using gas containing nitrogengas as the reactant gas, the nitrogen atoms bond to “dangling bonds”which exists in the carbon protective film, thereby increasing thechemical stability and mechanical strength of the carbon protective film

[0252] Additionally, in particular, when providing a lubricating film onthe carbon protective film, by means of using a reactant gas containingnitrogen gas, the wetting properties on the surface of the carbonprotective film are improved due to the introduction of the nitrogenpolar groups. Accordingly, the affinity of the carbon protective film tothe lubricating film improves, leading to improved durability of themagnetic recording medium

[0253] The reason for setting the adding volume of nitrogen gas to themixed gas in the aforementioned range is that if the adding volume isless than the aforementioned range, the aforementioned effects becomeinsufficient, while if the adding volume exceeds the aforementionedrange, the nitrogen content in the carbon protective film becomes toohigh, leading to a decrease in the strength of the carbon protectivefilm, and inferior durability

[0254] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 46 and 47

[0255] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0 8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film (with a thickness of 600 Å) comprising a Cralloy, and a magnetic film comprising a Co alloy were successivelyformed on both sides of the substrate, using a spattering device (3010manufactured by Anelva), to obtain a disc D.

[0256] Subsequently, the disc D was transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and a reactant gas was suppliedfrom the supply source 14 into the chamber to achieve a flow rate of 130sccm.

[0257] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 10 by volume, into which nitrogen gas wasadded at a adding volume shown in Table 6, was used as the reactant gasFurthermore, the inner pressure of the chamber 10 was maintained at 6 Pa

[0258] At the same time, high frequency electrical power of 500 W wassupplied to the electrodes 11 to generate plasma, and thereby form thecarbon protective film with a thickness of 50 Å on both sides of thedisc D At this time, high frequency electrical power of 50 W was appliedto the disc D, using the electrical bias source 13. In addition, thedifference in the phase of high frequency electrical power supplied toeach electrode 11 was set at 180°

[0259] Subsequently, fomblin lubricant was applied to the carbonprotective film, to form a lubricating film with a thickness of 15 Å,thereby yielding the magnetic recording medium.

[0260] The CSS test and corrosion test the following were performed onthe magnetic recording media

[0261] In the CSS test, using an MR head, a CSS operation was performed20,000 times at a rotational speed of 7200 rpm, and a temperature of 40°C. with a humidity of 80%. The dynamic stiction value was monitoredafter allowing the magnetic recording medium to sit for one hour

[0262] In the corrosion test, after sitting for 96 hours at a hightemperature (60° C.) and high humidity (80%), the magnetic recordingmedium was soaked in 50 cc of ultrapure water at 25° C., and theextraction amount of Co (per substrate area) from the ultrapure waterwas measured In addition, the extraction amount of Co was measured inthe same manner after allowing the magnetic recording medium to sit for96 hours at normal temperature (25° C.) and normal humidity (50%) Thesetest results are shown in Table 6.

Test Examples 48 and 49

[0263] Magnetic recording medium was manufactured, using a gas, in whichnitrogen gas had been added into a mixed gas at a adding volume shown inTable 6, as the reactant gas The CSS test and corrosion test wereperformed on the magnetic recording media These test results are alsoshown in Table 6 TABLE 6 Adding Corrosion Test vol. of Normal Highnitrogen Coating temp. & temp. & gas Stiction rate humidity humidity(vol. %) (−) (Å/min) (ng/cm²) (ng/cm²) Test Example 46 50 0.88 664 0.070.34 Test Example 47 100 0.67 432 0.11 0.25 Test Example 48 0 1.27 7530.12 0.24 Test Example 49 200 Crash 125 0.44 1.25

[0264] From Table 6, it is clear that the magnetic recording mediamanufactured according to a method which used a mixed gas, into whichnitrogen gas was added at a adding volume of 0 1˜100% of the mixed gas,as the reactant gas, exhibited lower stiction values, leading to asuperior durability. Additionally, from the results of the corrosiontest, it is clear that these magnetic recording media contained only anextremely small amount of corrosion, and exhibited a level of resistanceto corrosion which poses no problem for practical use.

[0265] As explained in the aforementioned, in the method formanufacturing a magnetic recording medium according to the presentinvention, it is possible to form a carbon protective film comprising asuperior durability. Accordingly, it is possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and hence reduce spacing loss

[0266] Thus, it is possible to provide a highly reliable magneticrecording medium, which can support a sufficiently high recordingdensity without lowering the output properties thereof

[0267] In the following, an embodiment of the magnetic recording mediumaccording to the present invention is described FIG. 4 shows anembodiment of the magnetic recording medium according to the presentinvention, wherein a non-magnetic base film 41, magnetic film 42, carbonprotective film 43, and lubricating film 44 are successively formed on anon-magnetic substrate S

[0268] The non-magnetic substrate S may comprise any substrate that isgenerally used as a substrate for a magnetic recording medium, examplesof which may include an aluminium alloy substrate coated with a NiPmetal film, and substrates comprising glass, silicone, and the like.

[0269] In addition, the surface of the non-magnetic substrate S ispreferably treated with texture-processing, e.g., mechanicaltexture-processing In particular, the average surface roughness (Ra) ispreferably in the range of 1˜20 Å

[0270] Preferred examples of the materials for the non-magnetic basefilm 41 and magnetic film 42 are as described in the aforementioned

[0271] The thickness of the non-magnetic base film 41 and magnetic film42 is preferably in the range of 50˜1000 Å, and 50˜800 Å, respectively.

[0272] In the magnetic recording medium according to the presentinvention, the carbon protective film may comprise a two-layerstructure, comprising a plasma CVD carbon layer 43 a formed according toa plasma CVD method, and a spatter carbon layer 43 b formed thereonaccording to a spatter-coating method

[0273] The thickness of a plasma CVD carbon layer 43 a is preferably inthe range of 30˜100 Å

[0274] A thickness of less than 30 Åresults in an insufficient strengthfor the entire protective film, while a thickness exceeding 100 Åresults in a magnetic recording medium with a greater spacing loss atthe time of recording and replay, which leads to a higher likelihood oflowering output properties when increasing recording density

[0275] The spatter carbon layer 43 b is provided on the surface of thecarbon protective film 43, and its thickness is in the range of 5˜100 Å,and preferably 30˜10 Å

[0276] A thickness of less than 30 Å results in weakening of the bondsbetween the spatter carbon layer 43 b and lubricating film 44, leadingto an inferior resistance to sliding of the magnetic recording medium Onthe other hand, a thickness exceeding 100 Å results in a decrease in theoutput properties at the time of increasing recording density

[0277] Preferred examples of the materials of the lubricating film 44may include perfluoropolyether, fomblin lubricant, and the like Thethickness of the lubricating film 44 is preferably 5˜40 Å

[0278] In the following, another embodiment of the method formanufacturing a magnetic recording medium according to the presentinvention is described, using an example in which an aforementionedmagnetic recording medium is manufactured.

[0279]FIG. 5 shows the spatter equipment used for manufacturing theaforementioned magnetic recording medium, which comprises a chamber 50;targets 51, which are provided on the inner walls on both sides of thechamber 50, an electrical source 52 which supplies electrical power tothe targets 51; a supply source 53 for spatter gas which suppliesspatter gas into the chamber 50.

[0280] The chamber 50 is connected to a introduction tube 54 whichdirects the spatter gas supplied from the supply source 53 into thechamber 50, and an exhaust tube 55 which expels gas inside of thechamber 7 out of the system.

[0281] The target 51 may principally comprise carbon

[0282] The electrical source 52 may comprise a D.C electrical source, ora high frequency electrical source.

[0283] In order to manufacture the aforementioned magnetic recordingmedium using the aforementioned spatter equipment and plasma CVDapparatus shown in FIG. 1, a non-magnetic base film 41 comprising a Cralloy, and magnetic film 42 comprising a Co alloy are successivelyformed on both sides of an aluminium alloy substrate S coated with a NiPmetal film, according to a method such as a spatter-coating method, toobtain a disc D.

[0284] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to the reactant gas, which is supplied from the supply source14 via the introduction tube 15 into the chamber 10, from which gas isexhausted via the exhaust tube 16 to circulate the gas within.

[0285] The reactant gas is preferably a mixed gas of hydrocarbon andhydrogen, with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume, and the hydrocarbon preferably comprises atleast one type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons

[0286] When carrying out this operation, the flow rate of the reactantgas is preferably 50˜500 sccm. Additionally, the inner pressure of thechamber 10 is preferably set at a predetermined value, such as 0.1˜10Pa.

[0287] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a plasma CVDcarbon layer 43 a, the thickness of which is preferably in the range of30˜100 Å, is formed on both sides of the disc D by means of plasmachemical gas phase growth, using the aforementioned reactant gas as astarting material.

[0288] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improvethe coating rate and durability of the protective film The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and more preferably comprises the oppositephase (i.e., 180°)

[0289] In addition, it is preferable to form the film while performingbias applying, such as high frequency bias or pulse D C bias, to thedisc D, using the electrical bias source 13 When using high frequencyelectrical source as the electrical bias source 13, high frequencyelectrical power of 10˜300 W is preferably applied to the disc DAdditionally, when using pulse D.C electrical source as the electricalbias source 13, a voltage of −400˜−10 V is preferably applied to thedisc D. Furthermore, the width of pulse is preferably in the range of10˜50000 ns, and the frequency is preferably in the range of 10 kHz 1GHz

[0290] The resultant plasma CVD carbon layer 43 a contains a highercontent of diamond-like carbon (DLC) of an increased hardness, and issuperior in strength, when compared to the carbon films formed accordingto the conventionally known, spatter-coating method

[0291] Subsequently, the disc D, on the surface of which a plasma CVDcarbon layer 43 a has been formed according to the aforementionedoperation, is transported into the chamber 50 of the spatter equipment,and the surface of the plasma CVD carbon layer 43 a, formed on theaforementioned disc D, is exposed to the spatter gas, which is suppliedinto chamber 50 from the supply source 53 via the introduction tube 54.Gas is then exhausted via the exhaust tube 55 to circulate the gaswithin.

[0292] The spatter gas may comprise argon, which is generally used inthe spatter-coating method In particular, a mixed gas comprising argon,into which at least one gas selected from among nitrogen, hydrogen, andmethane is added at a adding volume to the argon of 0 1˜100% by volume,is preferred.

[0293] At the same time, electrical power is supplied to target 51,using the electrical source 52, and the material of target 51 is thensupplied onto the plasma CVD carbon layer 43 a by means of spattering,to form the spatter carbon layers 43 b on both sides of the disc D

[0294] In this operation, the flow rate of the spatter gas is preferably20˜300 sccm.

[0295] Subsequently, a lubricant such as perfluoropolyether, fomblinlubricant, and the like, is applied to the spatter carbon layer 43 b,according to a dipping method or the like.

[0296] In this manner, a magnetic recording medium, which comprising anon-magnetic base film 41, magnetic film 42, carbon protective layer 43which comprises plasma CVD carbon layer 43 a and spatter carbon layer 43b, and lubricating layer 44 are successively formed on the substrate S,is provided

[0297] In the aforementioned magnetic recording medium, since the carbonprotective layer 43 is provided with a plasma CVD carbon layer 43 aformed according to a plasma CVD method, and spatter carbon layer 43 bformed according to a spatter-coating method, the adhesion of thelubricating film 44 to the carbon protective film 43 is increased, whichleads to a superior durability

[0298] It is hypothesized that the spatter carbon layer 43 b formed bymeans of spattering has a greater number of “dangling bonds” whencompared to the carbon film formed according to the plasma CVD method.Therefore, bonding which involves the “dangling bond” creates a strongeradhesion to the lubricating film 44, and thus leads to the superiordurability of the aforementioned magnetic recording medium

[0299] In addition, since the carbon protective layer 43 possesses aplasma CVD carbon layer 43 a of superior strength, it is possible tomake the carbon protective film 43 thinner while also maintaining thedurability, and thus reduce spacing loss In addition, it is possible toprevent problems such as “spin-off” in CSS operation

[0300] Accordingly, it is possible to provide effects of reliability anda sufficiently high recording density, without lowering the outputproperties thereof

[0301] Furthermore, in the aforementioned embodiment, the carbonprotective layer 43 is provided with a two-layer structure comprisingthe plasma CVD carbon layer 43 a and spatter carbon layer 43 b. However,the magnetic recording medium according to the present invention is notlimited thereto, and may also comprise a structure possessing three ormore layers.

[0302] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 50˜52

[0303] A magnetic recording medium was manufactured as follows, usingthe plasma CVD apparatus and spatter equipment shown in FIGS. 1 and 5.

[0304] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 41 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 42 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc D.

[0305] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a reactant gas was supplied from thesupply source 14 into the chamber to achieve a flow rate of 130 sccm

[0306] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 10 by volume, was used as the reactant gasAdditionally, the inner pressure of the chamber 10 was maintained at 6Pa.

[0307] At the same time, high frequency electrical power of 500 W wassupplied to the electrodes 11 to generate plasma, and thereby form aplasma CVD carbon layer 43 a with a Thickness of 40 Å on both sides ofthe disc D At this time, pulse D.C. bias of −120 V (with a frequency of200 kHz and pulse width of 500 ns) was applied to the disc, using theelectrical bias source 13 Furthermore, the temperature of the disc D atthe time of coating was maintained at 150° C. The difference in thephase of high frequency electrical power supplied to each electrode 11was set at 180° In addition, the distance between the disc D andelectrode 11 was set at 30 mm.

[0308] Subsequently, the disc D, on the surface of which the plasma CVDcarbon layer 43 a was formed according to the aforementioned operation,was transported into the chamber 50 of the spatter equipment, and thespatter gas supplied from the supply source 53 was directed into thechamber 50 via the introduction tube 54.

[0309] Spatter gas containing the respective components shown in Table 7was used herein

[0310] At the same time, electrical power was supplied to the target 51,using the electrical source 52, and the spatter carbon layers 43 b wereformed on both sides of the disc D, by means of spattering

[0311] Subsequently, a fomblin lubricant (Fomblin Zdol 2000) was appliedonto the spatter carbon layer 43 b, according to a dipping method, and alubricating film 44 with a thickness of 20 Å was formed, therebyyielding a magnetic recording medium.

[0312] The “bonded ratio” test, “spin-off” test, and CSS test describedin the following were performed on resultant magnetic recording media

[0313] (1) Bonded Ratio Test

[0314] The aforementioned magnetic recording medium was soaked in asolvent (AK225 manufactured by Asahi Glass) for 15 minutes, and thenremoved The ratio of the thickness of the lubricating film 44 prior tothis operation and after this operation was then calculated inpercentage The thickness of the lubricating film 44 was measured at theposition where the radius was 20 mm, using ESCA

[0315] (2) Spin-off Test

[0316] The aforementioned magnetic recording medium was rotated at arotational speed of 10000 rpm and a temperature of 100° C. for 168 hoursThe ratio of the thickness of the lubricating film 44 prior to thisoperation and after this operation was then calculated in percentage Thethickness of the lubricating film 44 was measured at the positions,where the radius of the magnetic recording medium was 20 mm (innercircumference, and 42 mm (outer circumference), using FT-IR

[0317] (3) CSS Test

[0318] Using an MR head, a CSS operation was performed on theaforementioned magnetic recording medium 80000 times, at a rotationalspeed of 7200 rpm, and a temperature of 40° C. at a humidity of 80%.

[0319] These test results are shown in Table 7

Test Examples 53 and 54

[0320] A carbon protective film was formed according to only a plasmaCVD method, based on the methods in Test Examples 50˜52, to provide amagnetic recording medium comprising a carbon protective film comprisinga single-layer structure (Test Example 53)

[0321] In addition, a carbon protective film was formed according to aconventionally known, spatter-coating method, to provide a magneticrecording medium comprising a carbon protective film comprising asingle-layer structure (Test Example 54)

[0322] The aforementioned three types of tests were performed on thesemagnetic recording media These test results are shown in Table 8

[0323] In the tables, the plasma CVD carbon layer is represented as“pCVD layer”, and the spatter carbon layer is represented as “spatterlayer” TABLE 7 Spin-off Spin-off Structure Thick- Thick- Inner Outer ofness of ness of Bonded circum- circum- protective pCVD spatter Spatterratio ference ference film layer (Å) layer (Å) gas (%) (%) (%) CSS TestTwo-layer 40 10 100% Ar 38 58 64 No Example 50 crash Test Two-layer 4010 98% Ar 46 65 74 No Example 51 and 2% crash N₂ Test Two-layer 40 1090% Ar 16 48 55 No Example 52 and 10% crash CH₄

[0324] TABLE 8 Spin-off Spin-off Structure Coating Thick- Inner Outer ofmethod ness of Bonded circum- circum- protective of carbon spatterSpatter ratio ference ference film film layer (Å) gas (%) %) (%) CSSTest Single- pCVD 50 — 20 37 43 Crash Example 53 layer Test Single-Spatter- 100 100% Ar 42 77 84 Crash Example 54 layer coating

[0325] From the results of the CSS test shown in Tables 7 and 8, it isclear that the magnetic recording media in which the carbon protectivefilm 43 comprised a two-layer structure comprising the plasma CVD carbonlayer 43 a and spatter carbon layer 43 b exhibited sufficient durabilityagainst CSS operation performed over 80000 times, whereas the magneticrecording media in which the carbon protective film comprised asingle-layer structure formed according to only a plasma CVD method, orspatter-coating method, led to “head crash”

[0326] Additionally, from the results of the bonded ratio test andspin-off test, it is clear that the magnetic recording medium whereinthe carbon protective film 43 comprised a two-layer structure exhibiteda lower reduction ratio of the thickness of the lubricating film,compared to the magnetic recording medium wherein the carbon protectivefilm was formed only according to the plasma CVD method.

[0327] Accordingly, the magnetic recording media in which the carbonprotective film 43 comprised a two-layer structure exhibited a superiordurability when compared to the magnetic recording medium in which thecarbon protective layer comprised a single-layer structure formedaccording to only a plasma CVD method, or spatter-coating method.

[0328] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film with asuperior durability. As a result, it is also possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss

[0329] Therefore, it is possible to provide a highly reliable magneticrecording medium, which is capable of sufficiently increasing recordingdensity without lowering the output properties thereof.

[0330] In the following, another embodiment of the method ofmanufacturing the magnetic recording medium according to the presentinvention, using an example in which the plasma CVD apparatus shown inFIG. 1 is employed

[0331] Initially, a non-magnetic base film and magnetic film arerespectively formed on both sides of the non-magnetic substrateaccording to a method such as a spatter-coating method, and the like, toobtain a disc D

[0332] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for magnetic recording medium as describedin the aforementioned The material and thickness of the non-magneticbase film and magnetic film are as described in the aforementioned

[0333] In the method for manufacturing the magnetic recording mediumaccording to the present embodiment, the process of coating the carbonprotective film comprises two subsequent processes as described in thefollowing

[0334] As the first process, the following operation is performed

[0335] The disc D, wherein the non-magnetic base film and magnetic filmare formed on the aforementioned non-magnetic substrate, is transportedinto the chamber 10 of the plasma CVD apparatus, and the surface of thedisc D is exposed to the reactant gas, which is supplied from the supplysource 14 through the introduction tube 15 into the chamber 10. The gasis then exhausted from chamber 10 via the exhaust tube 16 to circulatethe gas therein.

[0336] The reactant gas is, as described in the aforementioned,preferably a mixed gas of hydrocarbon and hydrogen, with a mixing ratioof hydrocarbon to hydrogen in the range of 2 to 1˜1 to 100 by volume.The hydrocarbon preferably comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons.

[0337] In this operation, the flow rate of the reactant gas ispreferably in the range of 50˜500 sccm. Additionally, the inner pressureof the chamber 10 is preferably set at a predetermined value such as 01˜10 Pa

[0338] At the same time, high frequency electrical power of preferably50˜2000 W is supplied to electrodes 11, using a high frequencyelectrical source 12, to generate plasma, and the first carbon layerhaving a thickness of preferably 30˜45 Å is formed on both sides of thedisc D by means of plasma chemical gas phase growth, using theaforementioned reactant gas as a starting material.

[0339] In this first process, at this point, bias such as high frequencybias or pulse D C bias is applied to the disc D, to form the film bymeans of a bias electrical source 13

[0340] When using high frequency bias as the aforementioned bias, highfrequency electrical power of 10˜300 W is preferably applied to thedisc, using a high frequency electrical source as the bias electricalsource 13.

[0341] This is due to the fact that if bias applied to the disc D duringcoating is less than 10 W, the first carbon layer will contain a largeamount of high polymer components, which are inferior in strength, andthus reduce the durability. On the other hand, if the bias exceeds 300W, sparks are likely to occur during coating, which lead to a greaterlikelihood of creating abnormal growth sections on the surface of thefirst carbon layer

[0342] Additionally, when using pulse D.C bias as bias and pulse D.Celectrical source as the bias electrical source 13, a voltage of−400˜−10 V is preferably applied to the disc

[0343] This is due to the fact that if bias applied to the disc D duringcoating is less than −400 V, sparks are likely to occur at the time ofcoating, which lead to a greater likelihood of creating abnormal growthsections on the surface of the first carbon layer If the bias exceeds−10 V, the first carbon layer contains a higher content of high polymercomponents, which are inferior in strength

[0344] In addition, preferably, the pulse width is in the range of10˜500 ns, and the frequency is in the range of 10 kHz˜1 GHz.

[0345] The resultant first carbon layer thereby contains a large amountof diamond-like-carbons (DLC) which exhibit an increased hardness.

[0346] The reason for preferably setting the thickness of the firstcarbon layer in the range of 30˜45 Å is due to the fact that a thicknessof less than 30 Å results in a reduction in the strength of the carbonprotective film, leading to a lower durability of the resultant magneticrecording medium; and a thickness exceeding 45 Å results in a magneticrecording medium that exhibits greater spacing loss at the time ofrecording and replay, which tends to lower output properties at the timeof increasing the recording density.

[0347] Subsequently, the second process described in the following isperformed

[0348] In the second process, bias applying to the disc D, using thebias electrical source 13, is halted, and a second carbon layer ofpreferably 5˜20 Å is formed onto the first carbon layer in a similarmanner as in the aforementioned first process, with the exception thatbias applying is not performed

[0349] The reason for setting the thickness of the second carbon layerin the range of 5˜20 Å is due to the fact that if the thickness is lessthan 5 Å, the joining strength between the second carbon layer andlubricating film weakens, leading to a lower resistance to sliding ofthe magnetic recording medium; while if the thickness exceeds 20 Å, theresultant magnetic recording medium exhibits greater spacing loss at thetime of recording and replay, which tends to lower output properties atthe time of increasing the recording density

[0350] In the aforementioned first and second processes, when supplyingelectrical power to the electrodes 11 and 11, the phase of theelectrical power supplied to each electrode 11 are preferably shiftedwith respect to each other. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improveboth the coating rate and durability of the protective film. Thedifference of the phase of electrical power supplied to each electrodeis preferably in the range of 90˜270°, and in particular, the oppositephase (i.e., 180°) is preferred.

[0351] Through the aforementioned first and second processes, the carbonprotective film comprising the first and second carbon layer is formedonto the disc D.

[0352] Subsequently, a lubricant such as perfluoropolyether, fomblinlubricant, and the like, is applied onto the second carbon layeraccording to a dipping method or the like, to form a lubricating filmwith a thickness of preferably 5˜40 Å

[0353] In this manner, a magnetic recording medium is obtained, whereina non-magnetic base film, magnetic film, a carbon protective film (firstcarbon layer and second carbon layer), and lubricating film aresuccessively formed

[0354] Examples of the magnetic recording medium manufactured accordingto the aforementioned manufacturing method may include a magneticrecording medium with a structure similar to that shown in FIG. 4

[0355] The magnetic recording medium of this example comprises anon-magnetic substrate S, non-magnetic base film 41, magnetic film 42,carbon protective film 43 (first carbon layer 43 a, and second carbonlayer 43 b), and lubricating film 44

[0356] In the aforementioned method for manufacturing a magneticrecording medium, the carbon protective film 43 is formed, by means offorming a second carbon layer 43 b, according to the plasma CVD methodwithout performing bias applying to the disc D, on top of a first carbonlayer 43 a, which is formed according to a plasma CVD method whileperforming bias applying to the disc D In this manner, the resultantmagnetic recording medium exhibits a higher bonding strength withrespect to the lubricating film 44, lying in contact with the secondcarbon layer 43 b of the carbon protective film 43, and hence leads to asuperior durability

[0357] The reason for the superior durability of the aforementionedmagnetic recording medium is as follows That is, the second carbon layer43 b, which is formed without performing bias applying to the disc D,contains a greater number of dangling bonds, compared to the firstcarbon layer 43 a which is formed while performing bias applying to thedisc D, and bonding which involves these dangling bond generates astronger adhesion to the lubricating film

[0358] In addition, the first carbon layer 43 a, which is formed whileperforming bias applying to the disc D contains a higher content ofdiamond-like-carbon (DLC), leading to a superior strength.

[0359] As a result, the carbon protective film 43 exhibits a higherstrength, and moreover is firmly joined to the lubricating film 44.Accordingly, it is possible to make the carbon protective film 43thinner while also maintaining a sufficient durability, and therebyreduce spacing loss Additionally, problems such as spin-off in the CSSoperation do not occur

[0360] Accordingly, it is possible to provide a highly reliable magneticrecording medium that is capable of increasing the recording densitysufficiently without lowering the output properties thereof

[0361] Furthermore, in the aforementioned embodiment, the carbonprotective film comprises a two-layer structure comprising a firstcarbon layer 43 a and second carbon layer 43 b. However, the magneticrecording medium according to the present invention is not limitedthereto, and may comprise a structure of three or more layers

[0362] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 55˜59

[0363] Magnetic recording medium was manufactured as described in thefollowing, using the plasma CVD apparatus shown in FIG. 1

[0364] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 41 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 42 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc DSubsequently, the disc D was transported into the chamber 10 of theplasma CVD apparatus, and a mixed gas was supplied from the supplysource 14 into the chamber to achieve a flow rate of 130 sccm

[0365] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 12 by volume, was used as the reactant gas.Additionally, the inner pressure of the chamber 10 was maintained at 6Pa.

[0366] At the same time, high frequency electrical power of 450 W wassupplied to the electrodes 11 to generate plasma, while applying pulseD.C. bias of −120 V (with a frequency of 200 kHz and a pulse width of500 ns) to the disc D, using the bias electrical source 13, to form thefirst carbon layer 43 a. The temperature of the disc D and coating rateat the time of coating were set at 130° C., and 450 Å/min, respectively.The difference in the phase of high frequency electrical power suppliedto each electrode 11 was set at 180° In addition, the distance betweenthe disc D and electrode 11 was set at 30 mm

[0367] Subsequently, a second carbon layer 43 b with a thickness shownin Table 9 was formed onto the disc D, onto which a first carbon layer43 a had been formed on the surface thereof as described in theaforementioned, according to the similar method for forming the firstcarbon layer 43 a, with the exception that bias was not applied to thedisc D.

[0368] Subsequently, a fomblin lubricant (Fomblin Zdol 2000) was appliedonto the second carbon layer 43 b, according to a dipping method, and alubricating film 44 with a thickness of 20 Å was formed, therebyyielding a magnetic recording medium

[0369] The bonded ratio test, spin-off test, and CSS test described inthe following were then performed on the resultant magnetic recordingmedia

[0370] (1) Bonded Ratio Test

[0371] The aforementioned magnetic recording medium was soaked in asolvent (AK225 manufactured by Asahi Glass) for 15 minutes, and thenremoved The ratio of the thickness of the lubricating film 44 prior tothis operation and after this operation was then calculated inpercentage Furthermore, the thickness of the lubricating film 44 wasmeasured at a position where the radius was 20 mm, using ESCA

[0372] (2) Spin-off Test

[0373] The aforementioned magnetic recording medium was rotated at arotational speed of 10000 rpm and a temperature of 100° C. for 168 hoursThe ratio of the thickness of the lubricating film 44 prior to thisoperation and after this operation was then calculated in percentage Thethickness of the lubricating film 44 was measured at the positions wherethe radius of the magnetic recording medium was 20 mm (innercircumference) and 42 mm (outer circumference), respectively, usingFT-IR.

[0374] (3) CSS Test

[0375] Using an MR head, a CSS operation was performed on theaforementioned magnetic recording medium 40000 times at a rotationalspeed of 7200 rpm, and a temperature of 40° C. with a humidity of 80%.

[0376] The test results are shown in Table 9.

Test Example 60

[0377] A magnetic recording medium was manufactured in the similarmanner as in the aforementioned test example, with the exception that asecond carbon layer 43 b was not formed

[0378] The resultant magnetic recording medium underwent with theaforementioned three types of tests The test results are shown in Table9

Test Example 61

[0379] A magnetic recording medium was manufactured, in which the carbonprotective film was formed according to a conventionally known,spatter-coating method

[0380] The aforementioned three types of tests were performed on theresultant magnetic recording medium The test results are shown in Table9 TABLE 9 Spin-off Spin-off CSS (the First carbon layer Second carbonlayer Inner Outer number) Thick- Thick- Bond circum- circum- of timesCoating ness Coating ness ratio ference ference a crash method (Å)method (Å) (%) (%) (%) occurred) Test pCVD 40 pCVD 10 19 56 61 No crashExample 55 (w/bias) (w/o bias) Test pCVD 32 pCVD 18 23 59 63 No crashExample 56 (w/bias) (w/o bias) Test pCVD 25 pCVD 25 25 64 70 CrashExample 57 (w/bias) (w/o bias) (37000) Test pCVD 12 pCVD 38 26 68 75Crash Example 58 (w/bias) (w/o bias) (25000) Test pCVD 47 pCVD  3 11 4045 Crash Example 59 (w/bias) (w/o bias) (20000) Test pCVD 50 — — 10 3844 Crash Example 60 (w/bias) (15000) Test Spatter- 50 — — 33 76 82 CrashExample 61 ing

[0381] From the results of the CSS test shown in Table 9, it is clearthat the magnetic recording media wherein the carbon protective film 43comprised a first and second carbon layers 43 a and 43 b exhibitedsuperior resistance to sliding, when compared to the magnetic recordingmedium wherein the carbon protective film comprised only a single-layerstructure

[0382] In particular, the magnetic recording media wherein the thicknessof the second carbon layer was 5˜20 Å exhibited sufficient durabilityagainst the CSS operation

[0383] Additionally, from the results of the bonded ratio test andspin-off test, it is clear that the magnetic recording media in whichthe carbon protective film 43 comprised a two-layer structure exhibiteda lower reduction ratio of the thickness of the lubricating film, whencompared to magnetic recording media wherein the carbon protective filmcomprised a single-layer structure

[0384] Accordingly, the magnetic recording media in which the carbonprotective film comprised a two-layer structure exhibited a superiordurability

[0385] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film with asuperior durability. Therefore, it is also possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss.

[0386] As a result, it is possible to provide a highly reliable magneticrecording medium, which is capable of sufficiently increasing therecording density without lowering the output properties thereof

[0387] In the following, another embodiment of the magnetic recordingmedium according to the present invention is described.

[0388] The magnetic recording medium of this embodiment may comprise asimilar structure to that shown in FIG. 4. The magnetic recording mediumaccording to this embodiment comprises a non-magnetic substrate S,non-magnetic base film 41, magnetic film 42, carbon protective film 43(first carbon layer 43 a, and second carbon layer 43 b), and lubricatingfilm 44

[0389] Examples of the non-magnetic substrate S may include an aluminiumalloy substrate coated with a NiP metal film, and substrates comprisingglass, silicone, and the like The surface of the substrate S ispreferably treated with texture-processing such as mechanicaltexture-processing. In particular, the average surface roughness (Ra) ispreferably in the range of 1˜20 Å. The material and thickness of thenon-magnetic base film 41 and magnetic film 42 are as described in theaforementioned

[0390] In the magnetic recording medium of the present embodiment, theprotective film 43 comprises a two-layer structure comprising a tantalumnitrogen layer 43 a and carbon layer 43 b formed thereon

[0391] The tantalum nitrogen layer 43 a comprises titanium and nitrogen,incorporating a material comprising a nitrogen content of 1˜30 at % asits main component

[0392] A nitrogen content of less than 1 at % results in a loss ofstrength of the protective film 43, leading to a lower durability of theresultant magnetic recording medium Additionally, a nitrogen contentexceeding 30 at % also results in a decrease in the strength of theprotective film 43, similarly leading to a lower durability of theresultant magnetic recording medium.

[0393] The tantalum and nitrogen in the tantalum nitrogen layer 43 aexist in the form of TaN, Ta₂N, Ta₃N₅, simple substance, or mixturethereof

[0394] The thickness of the tantalum nitrogen layer 43 a is preferablyin the range of 1˜95 Å.

[0395] A thickness of less than 1 Å results in a protective filmcomprising an inadequate strength, while a thickness exceeding 95 Åresults in a magnetic recording medium that exhibits greater spacingloss at the time of recording and replay, leading to a likelihood oflowering the output properties at the time of increasing the recordingdensity

[0396] The carbon layer 43 b is formed according to the plasma CVDmethod

[0397] The thickness of the carbon layer 43 b is preferably in the rangeof 5˜100 Å

[0398] If the thickness is less than 5 Å, the bond between the carbonlayer 43 b and lubricating film 44 weakens, leading to a lowerresistance to sliding of the magnetic recording medium On the otherhand, a thickness exceeding 100 Å results in a decrease in the strengthof the protective film 43

[0399] The lubricating film 44 preferably comprises a lubricant such asperfluoropolyether, fomblin lubricant, and the like The thickness of thelubricating film is preferably in the range of 5˜40 Å

[0400] In the following, another embodiment of the method formanufacturing magnetic recording medium according to the presentinvention is described, using an example in which the aforementionedmagnetic recording medium is manufactured

[0401] In the manufacturing method according to the present embodiment,a spattering device is employed with a similar structure to that shownin FIG. 5, with the exception that a material comprising principallytantalum, or a mixture of tantalum and nitrogen is used as the target 51

[0402] D C electrical source or high frequency electrical source may beused as the electrical source 52 Preferred examples of the D Celectrical source may include one that is capable of supplying anelectrical power of 50˜6000 W to the target 51

[0403] In order to manufacture the aforementioned magnetic recordingmedium, using the aforementioned spattering device, and the plasma CVDapparatus shown in FIG. 1, a non-magnetic base film 41 comprising a Cralloy or the like, and a magnetic film 42 comprising a Co alloy or thelike are successively formed on both sides of the aluminium alloysubstrate S coated with a NiP metal film, according to a method such asa spatter-coating method, to obtain a disc D.

[0404] Subsequently, the disc D is transported into the chamber 50 ofthe aforementioned spattering apparatus, and the surface of the disc Dis exposed to the spatter gas, which is supplied from the supply source53 through the introduction tube 54 into the chamber 50, from which thegas is exhausted via the exhaust tube 55 to circulate the gas within.

[0405] Examples of the spatter gas may include any gas described below

[0406] When using a target principally comprising tantalum as the target51, a gas formed from Ar or the like, which is generally used in thespatter-coating method, into which a nitrogen gas has been added atadding volume of 0 1˜100 vol % of said gas, may be used.

[0407] Furthermore, when using a target principally comprising tantalumand nitrogen as the target 51, a gas such as Ar, or similar gas to whichan appropriate amount of nitrogen has been added, may be used.

[0408] At the same time, electrical power is supplied to the target 51,using the electrical source 52, and the material of the target 51further is supplied onto the disc D'by means of spattering, to form atantalum nitrogen layer 43 a, which comprises a material comprisingtantalum and nitrogen as its main component, on both side of the disc D

[0409] In this operation, the flow rate of the spatter gas is preferablyin the range of 10˜200 sccm

[0410] Subsequently, the disc D comprising a tantalum nitrogen layer 43a is transported into the chamber 10 of the plasma CVD apparatus, andthe surface of the disc D is exposed to a reactant gas, which issupplied from the supply source 14 through the introduction tube 15 intothe chamber 10. The gas is then exhausted from chamber 10 via theexhaust tube 16 to circulate the gas therein

[0411] The reactant gas is preferably a mixed gas of hydrocarbon andhydrogen, with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume, and the hydrocarbon preferably comprises atleast one type of hydrocarbon selected from among lower saturatedhydrocarbons,,lower unsaturated hydrocarbons, and lower cyclichydrocarbons.

[0412] In this operation, the flow rate of the reactant gas ispreferably in the range of 50˜500 sccm. Additionally, the inner pressureof the chamber 10 is preferably set at a predetermined value such as0.1˜10 Pa.

[0413] At the same time, high frequency electrical power of preferably50˜2000 W is supplied to the electrodes 11, using the high frequencyelectrical source 12, to generate plasma, and thereby form a carbonlayer 43 b with a thickness of preferably 5˜10 Å on both sides of thedisc D, by means of plasma chemical gas phase growth, using theaforementioned reactant gas as a starting material

[0414] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different By means of making the phases of electrical powersupplied to each electrode 11 different, it is possible to improve thecoating rate and durability of the protective film. The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular, more preferably oppositephase (i e, 180°)

[0415] The resultant carbon layer 43 b contains a higher content ofdiamond-like-carbons (DLC), which exhibit an increased hardness, leadingto a superior strength when compared to a carbon film formed accordingto the conventionally known, spatter-coating method

[0416] In this operation, it is preferable to form the film whileperforming bias applying e.g, high frequency bias and pulse D.C bias tothe disc D, using the bias electrical source

[0417] The conditions such as the voltage of the bias are preferably setas described in the aforementioned

[0418] Subsequently, a lubricant such as perfluoropolyether, fomblinlubricant, and the like, is applied onto the carbon layer 43 b,according to a dipping method, and the like, to form a lubricating film44 In this manner, a magnetic recording medium is provided wherein anon-magnetic base film 41 and magnetic film 42 are first formed onto asubstrate S, followed by successive formation of a protective film 43,comprising a tantalum nitrogen layer 43 a and a carbon layer 43 b, and alubricating film 44 thereon.

[0419] In the aforementioned magnetic recording medium, the protectivefilm 43 is provided with the carbon layer 43 b, which is formed on atantalum nitrogen layer 43 a, consisting principally of a materialcomprising tantalic and nitrogen, according to a plasma CVD method, andthus exhibits a superior durability.

[0420] The reason that the aforementioned magnetic recording mediumexhibits a superior durability can be attributed to the formation of aprotective film 43 comprising a carbon layer 43 b, which exhibitssufficient strength and relatively high bonding strength with thelubricating film 44, onto a tantalum nitrogen layer 43 a which exhibitsa great hardness

[0421] Accordingly, it is possible to make the protective film 43thinner while also maintaining a sufficient durability, and therebyreduce spacing loss

[0422] Therefore, it is possible to provide a magnetic recording medium,that is reliable and capable of sufficiently increasing the recordingdensity without lowering the output properties thereof

[0423] Furthermore, in the aforementioned embodiment, the protectivefilm 43 is provided with a two-layer structure comprising a tantalumnitrogen layer 43 a and a carbon layer 43 b However, the magneticrecording medium according to the present invention is not limitedthereto, and may also comprise a structure having three or more layers

[0424] In the following, the effects of the present invention arespecified, using concrete examples.

Test Examples 62˜64

[0425] A magnetic recording medium was manufactured, using theaforementioned plasma CVD apparatus, and spattering device, according tothe following process A spattering device with a target 51 comprisingtantalum was used

[0426] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0 8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 41 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 42 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc D.

[0427] Subsequently, the disc D was transported into chamber 50 of thespattering device, and a spatter gas was supplied from the supply source53 to the chamber 50 via the introduction tube 54

[0428] A mixed gas of nitrogen and argon, comprising a mixing ratioshown in Table 10, was used as the spatter gas. Additionally, the innerpressure of the chamber 50 was maintained at 0.7 Pa.

[0429] At the same time, D.C electrical power of 600 W was supplied tothe target 51, and a tantalum nitrogen layer 43 a comprising tantalumand nitrogen was formed on both sides of the disc D by means ofspattering

[0430] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a reactant gas was supplied from thesupply source 14 into the chamber 10

[0431] A mixed gas of toluene and hydrogen, comprising a mixing ratioshown in Table 10, was used as the reactant gas Additionally, the innerpressure of the chamber 10 was maintained at 6 Pa

[0432] At the same time, high frequency electrical power of 300 W wassupplied to the electrodes 11, to generate plasma, while applying highfrequency electrical power of 50 W (with a frequency of 13 56 MHz) tothe disc D, using the bias electrical source 13, to form a carbon layer43b on both sides of the disc D

[0433] Furthermore, the temperature of the disc D at the time of formingthe carbon layer 43 b was set at 130° C. The difference in the phase ofhigh frequency electrical power supplied to each electrode 11 was 180°.Additionally, the distance between the disc D and the electrode 11 wasset at 30 mm.

[0434] Subsequently, a fomblin lubricant (Fomblin Zdol 2000) was appliedonto the carbon layer 43 b, according to a dipping method, to form alubricating film 44 with a thickness of 20 Å, thereby yielding amagnetic recording medium

[0435] The CSS test described in the following was performed on theresultant magnetic recording media In the CSS test, using an MR head, aCSS operation was performed 20000 times at a rotational speed of 7200rpm, and a temperature of 40° C. with a humidity of 80% The dynamicstiction value was monitored after allowing the magnetic recordingmedium to sit for one hour. The results are shown in Table 10.

Test Example 65

[0436] A magnetic recording medium, wherein the protective filmcomprised a single-layer structure comprising only a carbon layer, wasmanufactured without forming a tantalum nitrogen layer

Test Example 66

[0437] A magnetic recording medium, wherein the protective filmcomprised a single-layer structure comprising only a tantalum nitrogenlayer, was manufactured without forming a carbon layer.

Test Example 67

[0438] A magnetic recording medium, wherein the protective filmcomprised a two-layer structure comprising a tantalum nitrogen layer anda carbon layer, was manufactured according to a method in which aspatter gas containing nitrogen, at a mixing ratio shown in Table 10,was used at the time of forming the tantalum nitrogen layer.

[0439] The aforementioned CSS test was performed on these magneticrecording media, and the test results are shown in Table 10

[0440] The nitrogen content in the tantalum nitrogen layer of themagnetic recording medium in each of the aforementioned Test Examples62, 63, 65, and 66 were 5 at % and the nitrogen content in the tantalumnitrogen layer of the magnetic recording medium in Test Example 67 was40 at % TABLE 10 Structure Tantalic nitrogen layer Carbon layer ofNitrogen content Thick- Flow rate of reactant gas Thick- protective inspatter gas ness Toluene Hydrogen ness Stiction film (vol. %) (Å) (sccm)(sccm) (Å) (−) Test Two-layer 5 45 10 120  5 0.67 Example 62 TestTwo-layer 5 10 10 120 40 0.44 Example 63 Test Two-layer 5 45 100   0  50.91 Example 64 Test Single- — — 10 120 50 1.27 Example 65 layer TestSingle- 5 50 — — — Crash Example 66 layer Test Two-layer 50  30 10 12020 Crash Example 67

[0441] From the results of the CSS test shown in Table 10, it is clearthat the magnetic recording media comprising a protective film 43comprising a tantalum nitrogen layer 43 a, with a nitrogen content of1˜30 at %, and carbon layer 43 b formed there on, exhibited sufficientdurability against a CSS operation performed 20000 times On the otherhand, the magnetic recording media comprising only a single-layer carbonprotective film, or alternatively comprising a protective film in whichthe nitrogen content of the tantalum nitrogen layer was out of theaforementioned range, exhibited an inferior durability.

[0442] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film with asuperior durability Therefore, it is also possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss

[0443] Thus, it is possible to provide a highly reliable magneticrecording medium which is capable of sufficiently increasing therecording density without lowering the output properties thereof

[0444]FIGS. 6 and 7 show the critical parts of the manufacturingequipment used in another embodiment of the method for manufacturingmagnetic recording medium according to the present invention. FIG. 6shows an ultraviolet ray irradiation device; and FIG. 7 shows a washingapparatus.

[0445] The ultraviolet ray irradiation device is used to irradiate thesurface of the carbon protective film with ultraviolet rays, and isprovided with a chamber 74 for storing a disc comprising a carbonprotective film; and ultraviolet ray source 75 for irradiating thesurface of the disc stored therein with ultraviolet rays The ultravioletray source is preferably one that is capable of irradiating ultravioletrays with a wavelength of 100˜400 nm.

[0446] Concrete examples of the ultraviolet ray source 75 may include anexcimer emission lamp.

[0447] The washing apparatus cleans the surface of the carbon protectivefilm of the disc, which has passed through the ultraviolet rayirradiation device, and is provided with a chamber 86 to store the disc;a supply source 87 for cleaning water to clean the disc stored in thechamber 86, and a nozzle 88 for injecting cleaning water supplied fromthe supply source 87 at the aforementioned disc.

[0448] In the following, another embodiment of the method formanufacturing magnetic recording medium according to the presentinvention is described, using an example in which the plasma CVDapparatus shown in FIG. 1 in addition to the aforementioned ultravioletray irradiation device and washing apparatus are employed

[0449] Initially, a non-magnetic base film and magnetic film are formedon both sates on non-magnetic substrate, according to thespatter-coating method and the like, to obtain a disc D

[0450] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for magnetic recording medium, asdescribed in the aforementioned The material and thickness of thenon-magnetic base film and magnetic film are as described in theaforementioned

[0451] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to a reactant gas, which is supplied from the supply source14 through the introduction tube 15 into the chamber 10. The gas is thenexhausted from chamber 10 via the exhaust tube 16 to circulate the gastherein.

[0452] The reactant gas is preferably a mixed gas of hydrocarbon andhydrogen, with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume, and the hydrocarbon preferably comprises atleast one type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons.

[0453] When carrying out this operation, the flow rate of the reactantgas is preferably 50˜500 sccm. Additionally, the inner pressure of thechamber 10 is preferably set at a predetermined value, such as 0.1˜10 Pa

[0454] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a carbonprotective film, with a thickness preferably in the range of 30˜10 Å, isformed on both sides of the disc D by means of plasma chemical gas phasegrowth, using the aforementioned reactant gas as a starting material.

[0455] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improvethe coating rate and durability of the protective film The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular, the opposite phase (i.e,180°) is preferred

[0456] In this operation, it is preferable to form the film whileperforming bias app; N in, such as high frequency bias or pulse D.C.bias, to the disc D, using the electrical bias source 13

[0457] The conditions of bias such as voltage and the like arepreferably as described n the aforementioned

[0458] The formed carbon protective film contains a higher content ofdiamond-like-carbons (DLC), which exhibit an increased hardness

[0459] In the method for manufacturing magnetic recording mediumaccording to the present embodiment, subsequently, the disc D formedwith the aforementioned carbon protective film is transported into thechamber 74 of the ultraviolet ray irradiation denice, and the surface ofthe carbon protective film of the aforementioned disc D is irradiatedwith ultraviolet rays comprising a wavelength of preferably 100˜400 nm,using the ultraviolet ray source 75

[0460] If the wavelength of the ultraviolet rays is less than 100 nm,energy loss becomes great, while if the wavelength exceeds 400 nm, theeffects of improving the properties of the carbon protective film 23 areinsufficient, and hence undesirable.

[0461] The preferred condition at the time of irradiating withultraviolet rays is an illuminance of 5˜50 mW/cm², and radiationduration of 2˜600 seconds

[0462] Subsequently, the disc D which has passed through the ultravioletrays irradiation device, is transported into the washing apparatus, andcleaning water supplied from the supply source 87 is injected at theaforementioned disc D, using a nozzle 88, to clean the surface of thecarbon protective film As the cleaning water used herein, a ultrapurewater with only a small unpurified content is preferred due to itssuperior effectiveness in cleaning the surface of the carbon protectivefilm.

[0463] Subsequently, a lubricant such as perfluoropolyether, fomblinlubricant, and the like, is applied, according to a dipping method orthe like, to the carbon protective film on the surface of the disc D,which has passed through the washing apparatus, to form a lubricatingfilm In this manner, a magnetic recording medium, wherein a non-magneticbase film, magnetic film, carbon protective film and lubricating filmare successively formed on a substrate, is obtained.

[0464] Examples of the magnetic recording medium manufactured accordingto the aforementioned manufacturing method may include a magneticrecording medium A, a similar structure to that shown in FIG. 2.

[0465] In the magnetic recording medium of this example, a non-magneticsubstrate S a non-magnetic base film 31, a magnetic film 32, a carbonprotective film 33, and a lubricating film 34 are provided.

[0466] In the aforementioned method for manufacturing a magneticrecording medium, since the surface of the carbon protective film 33 isirradiated with ultraviolet rays prior to forming the lubricating film34, the quality of the film surface is improved and the adhesion of thecarbon protective film 33 to the lubricating film 34 is increased,leading to a superior durability

[0467] The reason for the aforementioned magnetic recording mediumexhibiting a superior durability is attributed to the, following.Specifically, by the irradiation with ultraviolet rays, the shallow areaof the carbon protective film 33, near the surface, contains a largeamount of dangling bonds, and bonding involving this dangling bonds ofthe carbon protective film 33 firmly adheres to the lubricating film 34.

[0468] Accordingly, it is possible to make the carbon protective filmthinner, and thereby reduce spacing loss. In addition, it is possible toprevent problems such as spin-off during CSS operation

[0469] Thus, it is possible to provide a highly reliable magneticrecording medium, which is capable of increasing the recording densitywithout lowering the output properties thereof

[0470] Additionally, by means of using an excimer emission lamp as theultraviolet ray source 75, it is possible to obtain a high output usinga short pulse width, and thereby efficiently improve the quality of thecarbon protective film 33 surface

[0471] In addition, by means of washing the surface of the carbonprotective film 33 with water, it is possible to remove the impuritiesthat are attached to the surface of the carbon protective film 33, andthereby clean the film.

[0472] Thus, it is possible to prevent a reduction in the bondingstrength between the carbon protective film 33 and lubricating film 34due to impurities lying between the two films, which in turn preventsany reduction in the durability of the magnetic recording medium.

[0473] In addition, in the manufacturing method according to theaforementioned embodiment, after forming the carbon protective film, thesurface is irradiated with ultraviolet rays, and then washed using waterHowever, the method for manufacturing magnetic recording mediumaccording to the present invention is not limited thereto, and thewashing process may precede the process of irradiating with ultravioletrays, after forming the carbon protective film.

[0474] In addition, the surface of the carbon protective film may alsobe washed using, water without undergoing irradiation with ultravioletrays Furthermore, the surface of the carbon protective film may beirradiated with ultraviolet rays without being washed

[0475] Additionally, in the method for manufacturing magnetic recordingmedium according to the present invention, after forming the carbonprotective film, a tape-vanishing process, wherein micro-ridges on thesurface of the carbon protective film are scraped off, may also beperformed.

[0476] In the following, the effects of the present invention arespecified, using concrete examples.

Test Example 68

[0477] A magnetic recording medium was manufactured, using a plasma CVDapparatus, an ultraviolet ray irradiation device, and a washingapparatus shown in FIG. 1, 6, and 7, respectively, according to thefollowing process.

[0478] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 31 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 32 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc D.

[0479] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a mixed gas was supplied from the supplysource 14 into the chamber to achieve a flow rate of 130 sccm.

[0480] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 12 by volume, was used as the reactant gasAdditionally, the inner pressure of the chamber 10 was maintained at 6Pa

[0481] At the same time, high frequency electrical power of 450 W wassupplied to the electrodes 11 to generate plasma, while applying pulse DC bias of −120 V (with a frequency of 200 kHz and pulse width of 500 ns)to the disc, using the electrical bias source 13, to form a carbonprotective film 33 with a thickness of 50 Å on both sides of the disc DThe temperature of the disc D, and coating rate were maintained at 130°C., and 450 Å/min, respectively The difference in the phase of highfrequency electrical power supplied to each electrode 11 was set at 180°In addition, the distance between the disc D and electrode 11 was set at30 mm

[0482] Subsequently, the disc D wherein the carbon protective film wasformed according to the aforementioned operation was transported intothe washing apparatus, wherein the surface was washed using ultrapurewater.

[0483] The disc D was then transported into the chamber 74, where thedisc D was irradiated with ultraviolet rays, using the ultraviolet raysource 75.

[0484] Herein, an excimer lamp (manufactured by Ushio Denki), which isable to irradiate ultraviolet rays of a wavelength of 172 mm (with ahalf band width of 14 nm), was used as the ultraviolet ray source 75,and ultraviolet ray irradiation was performed for 30 seconds at anilluminance of 10 mW/cm² under a nitrogen gas atmosphere.

[0485] Subsequently, the disc D was washed in the washing apparatusagain, and then a fomblin lubricant (Fomblin Zdol 2000) was applied 33after washing to the carbon protective film, according to a dippingmethod A lubricating film 34 with a thickness of 20 Å was then formed,to obtain a magnetic recording medium

Test Example 69

[0486] A magnetic recording medium was manufactured in the same manneras in Test Example 68, with the exception that an excimer lamp(manufactured by Ushio Denki) capable of irradiating ultraviolet rayswith a wavelength of 222 nm (with a half band width of 2 nm) was used asthe ultraviolet ray source 75, and the disc D was irradiated withultraviolet rays for 30 seconds at an illuminance of 7 mW/cm² under anitrogen gas atmosphere

Test Example 70

[0487] A magnetic recording medium was manufactured in the same manneras in Test Example 68, with the exception that the disc D was irradiatedwith ultraviolet rays under ambient air. ps Test Example 71

[0488] A magnetic recording medium was manufactured in the same manneras in Test Example 68, with the exception that the disc D was not washedin the washing apparatus In this test, ultraviolet ray source 75 used inTest Example 68 was used

Test Example 72

[0489] A magnetic recording medium was manufactured in the same manneras in Test Example 68 except that irradiation with ultraviolet rays wasnot performed

[0490] The bonded ratio test, spin-of test and CSS test described in thefollowing were performed on each magnetic recording medium, obtained ineach of the aforementioned Test Examples.

[0491] (1) Bonded Ratio Test

[0492] Each of the aforementioned magnetic recording medium was soakedin a solvent (AK225 manufactured by Asahi Glass) for 15 minutes, andthen removed The ratio of the thickness of the lubricating film 34 priorto this operation and after this operation was then calculated inpercentage. The thickness of the lubricating film 34 was measured at theposition where the radius measured 20 mm, using ESCA (3) Spin-off Test

[0493] The aforementioned magnetic recording medium was rotated at arotational speed of 10000 rpm and a temperature of 100° C. for 168 hoursThe ratio of the thickness of the lubricating film 34 prior to thisoperation and after this operation was then calculated in percentage.The thickness of the lubricating film 34 was measured at the positions,where the radius of the magnetic recording medium measured 20 mm (innercircumference) and 42 mm (outer circumference), respectively, usingFT-IR (3) CSS Test

[0494] Using an MR head, a CSS operation was performed on theaforementioned magnetic recording medium 5000 times, at a rotationalspeed of 7200 rpm, and a low temperature of 5° C. with a low humidity of15%

[0495] In this CSS test, two types of tests were performed in one test,the aforementioned magnetic recording medium was baked at a temperatureof 180° C. for 3 hours prior to the aforementioned CSS operation, and inthe other, no such baking process was performed The test results areshown in Table 11

Test Example 73

[0496] A magnetic recording medium was manufactured in the same manneras in Test Example 68 with the exception that neither irradiation usingultraviolet rays nor washing was performed

Test Example 74

[0497] A magnetic recording medium was manufactured in the same manneras in Test Example 68 with the exception that the carbon protective filmwith a thickness of 100 Å was formed according to a conventionallyknown, spattering method.

Test Example 75

[0498] A magnetic recording medium was manufactured in the same manneras in Test Example 74 with the exception that washing was not performed.

Test Example 76

[0499] A magnetic recording medium was manufactured in the same manneras in Test Example 74 with the exception that irradiation withultraviolet rays was not performed

Test Example 77

[0500] A magnetic recording medium was manufactured in the same manneras in Test Example 74 with the exception that neither irradiation usingultraviolet rays nor washing was performed.

[0501] The aforementioned three types of tests were performed on each ofthe aforementioned magnetic recording media. The test results are shownin Table 11

[0502] In the table, the plasma CVD method is referred to as “pCVDmethod”, and ultraviolet ray irradiation is referred to as “UVirradiation” TABLE 11 Carbon Spin-off Spin-off protective UV Inner OuterCSS film irradia- Bonded circum- circum- w/o With coating tion Washingratio ference ference baking baking method source process (%) (%) (%)process process Test pCVD Excimer with 33 74 80 No crash No crashExample 68 method lamp Test pCVD Excimer with 51 82 89 No crash No crashExample 69 method lamp Test pCVD Excimer with 39 77 83 No crash No crashExample 70 method lamp Test pCVD Excimer without 31 72 79 No crash Nocrash Example 71 method lamp Test pCVD — with 15 42 49 No crash No crashExample 72 method Test pCVD — without 11 38 44 No crash Crash Example 73method Test Spattering Excimer with 56 84 92 Crash Crash Example 74method lamp Test Spattering Excimer without 53 82 89 Crash Crash Example75 method lamp Test Spattering — with 30 75 82 Crash Crash Example 76method Test Spattering — without 28 76 82 Crash Crash Example 77 method

[0503] From the results of CSS shown in Table 11, it is clear that themagnetic recording media, manufactured according to a method in whichthe carbon protective film was formed according to the plasma CVDmethod, and ultraviolet ray irradiation and/or washing with ultrapurewater was performed prior to lubricating the film, exhibited sufficientdurability against CSS operations performed 5000 times

[0504] Additionally, from the results of the bonded ratio test andspin-off test, the magnetic recording media, manufactured according athe method in which UV irradiation was performed, exhibited a lowerreduction rate in thickness of the lubricating film, compared to thosemanufactured according to a method in which UV irradiation was notperformed.

[0505] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film of a superiordurability. As a result, it is also possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss

[0506] Consequently, it is possible to provide a highly reliablemagnetic recording medium, which is capable of sufficiently increasingthe recording density without lowering the output properties thereof

[0507] In the following, another embodiment of the magnetic recordingmedium according to the present invention is described

[0508] The magnetic recording medium according to the present embodimentcomprises a structure similar to that shown in FIG. 2 In the magneticrecording medium according to the present embodiment, a non-magneticsubstrate S, a non-magnetic base film 31, a magnetic film 32, a carbonprotective film 33, and a lubricating film 34 are provided

[0509] Examples of the non-magnetic substrate S may include an aluminiumalloy substrate coated with a NiP metal film, in addition to substratescomprising glass, silicone, and the like

[0510] The surface of the substrate S is preferably treated withtexture-processing such as mechanical texture-processing. In particular,the average surface roughness (Ra) is preferably in the range of 1˜20 Å

[0511] The material and thickness of the non-magnetic base film 31 andmagnetic film 32 are as described in the aforementioned. The thicknessof the non-magnetic base film 31 and magnetic film 32 are preferably inthe range of 50˜1000 Å, and 50˜800 Å, respectively

[0512] The carbon protective film 33 is formed according to the plasmaCVD method The thickness of the carbon protective film is preferably inthe range of 30˜100 Å

[0513] In the magnetic recording medium according to the presentembodiment, the lubricating film 34 principally comprises at least onecompound selected from among the compounds represented by the followingformula (1) through (5), number average molecular weight of which fallin the range of 500˜6000. The thickness of the lubricating film 34 ispreferably in the range of 5˜40 Å.

[0514] In this specification, the term “principally comprise” signifiesthat the particular component is contained in an amount greater than 70wt %

[0515] [wherein, m, n, p, q, r, s, t, u, v, and w represent an integer,respectively]

[0516] If the molecular weight of the compounds represented by theaforementioned formula (1) through (5) is less than 500, “spin-off”worsens On the other hand, if the molecular weight of the compoundsexceeds 6000, the lubricating ability of the surface of the resultantmagnetic recording medium deteriorates, undesirably leading to aninferior CSS property

[0517] Among the aforementioned, compounds represented by the formula(1) or (5), with a number average molecular weight of 500˜6000, areespecially preferred as the principal component of the lubricating film34, since these compound improve the spin-off properties and CSScharacteristics

[0518] Additionally, the lubricating film 34 may principally comprise amixture, wherein a compound represented by the following formula (6) ismixed into at least one compound selected from among the aforementionedformula (1) through (5), having a number average molecular weight is500˜6000, at a mixing ratio of 0 1˜20 wt %

[0519] [wherein, x represents an integer between 0˜6].

[0520] The formula (6) represents a compound, wherein six units of thestructure represented by (F—C₆H₄—O) and/or (O—C₆H₄—CF₃) are bonded to atleast one selected from among a nitrogen and/or phosphorus which havesix-member-ring structure

[0521] When using the compound represented by the formula (6), if theproportional content of this compound is less than 0.1 wt %, thelubricating ability of the surface of the resultant magnetic recordingmedium deteriorates, leading to an inferior CSS property. When theproportional content of the aforementioned exceeds 20 wt %, smearsderived from this compound tend to stick to the head, which isundesirable.

[0522] In the following, the method for manufacturing the aforementionedmagnetic recording medium is described.

[0523] In order to manufacture the aforementioned magnetic recordingmedium, initially, a non-magnetic base film 31 and magnetic film 32 wereformed on both sides of a non-magnetic substrate, according to a methodsuch as a spatter-coating method, or the like, to obtain a disc D.

[0524] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to a reactant gas, which is supplied from the supply source14 through the introduction tube 15 into the chamber 10, from which thegas is exhausted via the exhaust tube 16 to circulate the gas within

[0525] The reactant gas is a mixed gas of hydrocarbon and hydrogen, witha mixing ratio of hydrocarbon to hydrogen in the range of 2 to 1˜1 to100 by volume The hydrocarbon preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons

[0526] In this operation, the flow rate of the reactant gas ispreferably in the range of 50˜500 sccm Additionally, the inner pressureof the chamber 10 is preferably maintained at a predetermined value,such as 0 1˜10 Pa

[0527] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a carbonprotective film 33 with a thickness of preferably in the range of 30˜100Å, is formed on both sides of the disc D by means of plasma chemical gasphase growth, using the aforementioned reactant gas as a startingmaterial.

[0528] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improvethe coating rate and durability of the protective film. The differencein the phase of electrical power supplied to each electrode ispreferably in the range of 90˜270°, and in particular, the oppositephase (i.e., 180°) preferred

[0529] In this operation, it is preferable to form the film whileperforming bias applying, such as high frequency bias or pulse D.C.bias, to the disc D, using the electrical bias source 13.

[0530] The conditions of bias such as voltage and the like arepreferably as described in the aforementioned.

[0531] The resultant carbon protective film 33 contains a higher contentof diamond-like-carbons (DLC), which exhibit an increased hardness.

[0532] Subsequently, the lubricant comprising the compounds representedby the aforementioned chemical formula is applied to the carbonprotective film 33, according to a dipping method or the like, to form alubricating film 34 with a thickness of preferably 5˜40 Å In thismanner, a magnetic recording medium is obtained, in which thenon-magnetic base film 31, magnetic film 32, carbon protective film 33,and lubricating film 34 were successively formed on a substrate S

[0533] According to the aforementioned magnetic recording medium,wherein the lubricating film 34 principally comprises at least onecompound selected from among the compounds represented by formula (1)through (5), or alternatively principally comprises a mixture of theaforementioned compound and a compound represented by formula (6), inwhich the proportional content of the compound represented by theformula (6) is 0 1˜20 wt %, the aforementioned lubricating film 34exhibits a greater adhesion to the carbon protective film 33, and henceprovides for a superior durability

[0534] The reason for the aforementioned magnetic recording mediumexhibiting a superior durability is attributed to the fact that thelubricating film comprising the aforementioned components is firmlyadhered to the carbon protective film 33 formed according to the plasmaCVD method,

[0535] As a result, it is possible to make the carbon protective film 33thinner while also maintaining a sufficient durability, and therebyreduce spacing loss. Additionally, there are no problems such asspin-off in CSS operation.

[0536] Consequently, it is possible to provide a highly reliablemagnetic recording medium, which is capable of sufficiently increasingthe recording density without lowering the output properties thereof pIn the following, the effects of the present invention are specifiedusing concrete examples.

Test Examples 78˜84

[0537] The magnetic recording medium similar to that shown in FIG. 2 wasmanufactured as follows.

[0538] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0.8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 31 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 32 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc D

[0539] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a mixed gas was supplied from the supplysource 14 into the chamber 10 to achieve a flow rate of 130 sccm.

[0540] A mixed gas of toluene and hydrogen, with a mixing ratio oftoluene to hydrogen of 1 to 12 by volume, was used as the reactant gas,Additionally, the inner pressure of the chamber 10 was maintained at6Pa.

[0541] At the same time, high frequency electrical power of 450 W wassupplied to the electrodes 11 to generate plasma, while applying pulse DC bias of −120 V (with a frequency of 200 kHz and pulse width of 500 ns)to the disc, using the electrical bias source 13, to form a carbonprotective film 33 with a thickness of 50A on both sides of the disc DThe temperature of the disc D, and coating rate were maintained at 130°C., and 450 Å/min, respectively The difference in the phase of highfrequency electrical power supplied to each electrode 11 was set at180°. In addition, the distance between the disc D and electrode 11 wasset at 30 mm.,

[0542] Subsequently, a lubricating film 34 with a thickness of 20 Å,comprising the materials shown in Table 12, was formed on the carbonprotective film 33, according to a dipping method, to obtain a magneticrecording medium.

[0543] In the table, the numbers in parenthesis correspond to the numberof the aforementioned formula That is, for example, Fomblin ZTETRAOL2000 (1) used in Test Example 78 comprises the compound represented bythe aforementioned formula (1)

[0544] Additionally, in the magnetic recording medium in Test Example83, the lubricating film 34 comprises a mixture of Fomblin ZTETRAOL 2000(1) and Fomblin Zdol 2000 (4) (with a mixing ratio of 1 to 1 by volume)Additionally, in the magnetic recording medium in Test Example 84, thelubricating film 34 comprises the material in which X1P (6) was added toDemnum SP (2) at 3 wt%

[0545] The bonded ratio test, and CSS test described in the followingwere performed on the resultant magnetic recording media

[0546] (1) Bonded Ratio Test

[0547] The aforementioned magnetic recording medium was soaked in asolvent (AK225 manufactured by Asahi Glass) for 15 minutes, and thenremoved The ratio of the thickness of the lubricating film 34 prior tothis operation and after this operation was then calculated inpercentage The thickness of the lubricating film 34 was measured at theposition where the radius measured 20 mm, using ESCA

[0548] In addition, after the aforementioned bonded ratio test, themagnetic recording medium was left under the environment of atemperature of 120° C. for 3 hours, after which the bonded ratio testwas performed in the same manner The test results are shown in Table 12

[0549] In Table 12, the test results after thermal treatment at 120° C.are shown in the column of ‘with baking’, and the test results beforethermal treatment are shown in the column of ‘without baking’

[0550] (2) CSS Test

[0551] After the aforementioned magnetic recording medium was baked at atemperature of 120° C. for 3 hours, a CSS operation was performed, usingan MR head, on the aforementioned magnetic recording medium 10000 timesat a rotational speed of 7200 rpm, and a low temperature of 5° C. with alow humidity of 15%. The coefficient of dynamic friction on the surfaceof the magnetic recording medium was subsequently measured Furthermore,after the aforementioned magnetic recording medium was allowed to sitfor 6 hours, the coefficient of static friction was measured.

Test Examples 85˜88

[0552] A magnetic recording medium was manufactured, wherein the carbonprotective film was formed according to the spattering method, and thelubricating film comprised the materials shown in Table 12.

[0553] The aforementioned two types of tests were performed on thesemagnetic recording media The test results are shown in Table 12.

[0554] In the table, plasma CVD method is expressed as “pCVD” method.TABLE 12 Bonded ratio Coefficient Carbon without with Coefficient ofstatic protective film Material for baking baking of dynamic frictioncoating method lubricating film (%) (%) friction (−) (gram) Test PCVDmethod Fomblin 38 73 0.85 2.3 Example 78 ZTETRAOL 2000 (1) Test PCVDmethod Demnum SP (2) 10 33 1.41 3.8 Example 79 Test PCVD method DemnumSA (3) 11 42 1.27 3.3 Example 80 Test PCVD method Fomblin Zdol 15 580.90 2.2 Example 81 2000 (4) Test pCVD method Fomblin TX (5) 33 69 0.881.8 Example 82 Test pCVD method Fomblin 32 67 0.79 1.8 Example 83ZTETRAOL 2000 (1) + Fomblin Zdol 2000 (4) Test pCVD method Demnum SP 1032 0.59 2.5 Example 84 (2) + X1P (6) Test Spattering Fomblin 55 93 CrashCrash Example 85 method ZTETRAOL 2000 (1) Test Spattering Demnum SP (2)25 45 1.73 6.3 Example 86 method Test Spattering Fomblin Zdol 32 91Crash Crash Example 87 method 2000 (4) Test Spattering Demnum SP 23 420.87 4.1 Example 88 method (2) + X1P (6)

[0555] From the results of the CSS test shown in Table 12, it is clearthat the magnetic recording media, in which the carbon protective filmwas formed according to the plasma CVD method, and the lubricating filmprincipally comprised at least one compound selected from among theformula (1) through (5), or the aforementioned compound, into which acompound represented by the formula (6) is mixed in at 0.1˜20 wt %,maintained a small coefficient of dynamic friction, and exhibited adesirable resistance to sliding.

[0556] Accordingly, the aforementioned magnetic recording mediumexhibited a superior durability.

[0557] Additionally, the magnetic recording medium, wherein the carbonprotective film was formed according to the spattering method, induced ahead crash or exhibited an increased coefficient of static friction,from baking process at a high temperature. Whereas the magneticrecording medium, wherein the carbon protective film was formedaccording to the plasma CVD method, and the lubricating film principallycomprised the aforementioned compound(s), maintained a small coefficientof dynamic friction even after treatment at a high temperature.

[0558] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film with asuperior durability As a result, it is also possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss

[0559] Therefore, it is possible to provide a highly reliable magneticrecording medium, which is capable of sufficiently increasing therecording density without lowering the output properties thereof

[0560]FIG. 8 shows another embodiment of the magnetic recording mediumaccording to the present invention. In the magnetic recording mediumshown herein, a non-magnetic base film 61, magnetic film 62, and carbonprotective film 63 are successively formed on a non-magnetic substrate S

[0561] Examples of the non-magnetic substrate S may include an aluminiumalloy substrate coated with a NiP metal film, and substrates comprisingglass, silicone, and the like

[0562] In addition, the surface of the substrate S is preferably treatedwith texture-processing such as mechanical texture-processing Inparticular, the average surface roughness (Ra) is preferably in therange of 1˜20 Å

[0563] The material of the non-magnetic base film 61 and magnetic film62 are as described in the aforementioned. The thickness of thenon-magnetic base film 61 and magnetic film 62 are preferably in therange of 50˜1000 Å, and 50˜800 Å, respectively.

[0564] The carbon protective film 63 is formed according to the plasmaCVD method, and Co extraction amount to the substrate area is 3 ng/cm²or less, preferably 2 ng/cm² or less, or more preferably 1.5 ng/cm² orless.

[0565] Herein, the Co extraction amount represents the amount of Coextracted from water, at the time when the magnetic recording medium,wherein a protective film is formed on the magnetic film containing Coat 50 at % or greater, is left for 96 hours at a temperature of 60° C.and a humidity of 80%, and then soaked in the water at 20° C. for 30minutes.

[0566] If this Co extraction amount exceeds 3 ng/cm², the durability ofthe magnetic recording medium tends to weaken, which is undesirable

[0567] The thickness of the carbon protective film 63 is preferably inthe range of 30˜100 Å

[0568] If the thickness is less than 30 Å, the strength of the carbonprotective film 63 is inadequate, and if the thickness exceeds 100 Å,the resultant magnetic recording medium exhibits greater spacing loss atthe time of recording and replay, leading to a likelihood of loweringthe output properties at the time of increasing the recording density

[0569] Additionally, a lubricating film with a thickness of 5˜40 Å,comprising perfluoropolyether, fomblin lubricant, or the like, may beprovided on the carbon protective film 63.

[0570] In the following, the method for manufacturing the aforementionedmagnetic recording medium is described

[0571] When manufacturing the aforementioned magnetic recording medium,the plasma CVD apparatus shown in FIG. 1 may be used

[0572] In order to manufacture the aforementioned magnetic recordingmedium, using this equipment, initially, a non-magnetic base film 61comprising a Cr alloy or the like, and a magnetic film 62 comprising aCo alloy and the like are successively formed on both sides of anon-magnetic substrate S, comprising aluminium alloy coated with a NiPmetal film, according to a method such as the spatter-coating method,and the like, to obtain a disc D.

[0573] Subsequently, the disc D is transported into the chamber 10 ofthe aforementioned plasma CVD apparatus, and the surface of the disc Dis exposed to a reactant gas, which is supplied from the supply source14 through the introduction tube 15 into the chamber 10, from which thegas is exhausted via the exhaust tube 16 to circulate the gas within

[0574] The reactant gas is a mixed gas of hydrocarbon and hydrogen, witha mixing ratio of hydrocarbon to hydrogen in the range of 2 to 1˜1 to100 by volume. The hydrocarbon preferably comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons.

[0575] In this operation, the flow rate of the reactant gas ispreferably in the range of 50 500 sccm Additionally, the inner pressureof the chamber 10 is preferably maintained at a predetermined value,such as 0 1˜10 Pa

[0576] At the same time, using the high frequency electrical powersource 12, high frequency electrical power of preferably 50˜2000 W issupplied to the electrodes 11 to generate plasma, and a carbonprotective film 63 with a thickness of preferably in the range of 30˜100Å, is formed on both sides of the disc D by means of plasma chemical gasphase growth, using the aforementioned reactant gas as a startingmaterial

[0577] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improvethe coating rate and durability of the protective film The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular, more preferably oppositephase (i e, 180°)

[0578] In this operation, it is preferable to form the film whileperforming bias applying, such as high frequency bias or pulse D C bias,to the disc D, using the electrical bias source 13

[0579] The conditions of bias such as voltage and the like arepreferably as described in the aforementioned

[0580] The formed carbon protective film 63 contains a higher content ofdiamond-like-carbon (DLC), which exhibit an increased hardness, higherdensity and greater strength, wherein the Co extraction amount withrespect to the substrate area is 3 ng/cm² or less.

[0581] Subsequently, a lubricating film is preferably formed on thecarbon protective film 63 according to a dipping method, or the like, bymeans of applying a lubricant such as perfluoropolyether, fomblinlubricant, and the like.

[0582] The aforementioned magnetic recording medium, wherein a carbonprotective film 63 is formed according to the plasma CVD method, and theCo extraction amount to substrate area is 3 ng/cm2 or less, exhibits anincreased hardness and higher density, in addition to displayingsuperior strength and resistance to corrosion.

[0583] Accordingly, it is possible to make the carbon protective film 63thinner while also maintaining a sufficient durability, and therebyreduce spacing loss

[0584] Therefore, it is possible to provide a highly reliable magneticrecording medium, which is capable of sufficiently increasing therecording density without lowering the output properties thereof

[0585] In the following, the effects of the present invention arespecified, using concrete examples

Test Examples 89˜92

[0586] The magnetic recording medium shown in FIG. 8 is manufactured asfollows

[0587] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0 8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film 61 (with a thickness of 600 Å) comprising aCr alloy, and a magnetic film 62 comprising a Co alloy (Co₈₂Cr₁₅Ta₃)were successively formed on both sides of the substrate S, using aspattering device (3010 manufactured by Anelva), to obtain a disc D.

[0588] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a reactant gas was supplied from a supplysource 14 into the chamber A mixed gas comprising toluene and hydrogenwas used as the reactant gas The flow rate of each was as shown in Table13 Additionally, the inner pressure of the chamber 10 was maintained at6 Pa

[0589] At the same time, high frequency electrical was supplied to theelectrodes 11, power under the conditions shown in Table 13, to generateplasma, and a carbon protective film 63 with a thickness of 50 Å wasformed on both sides of the disc D, to yield a magnetic recording medium

[0590] At this time, pulse D.C. bias (DC) or high frequency bias (RF)was applied to the disc D, under the conditions shown in Table 13, usinga bias electrical source 13. Additionally, the temperature of the disc Dat the time of coating the film was set at 130° C. In addition, thedifference of the phase of high frequency electrical power supplied toeach electrode 11 was set at 180°. Additionally, the distance betweenthe disc D and electrodes 11 were set at 30 mm. In the table, plasma RFelectrical power represents the high frequency electrical power suppliedto the electrodes 11.

[0591] The Co extraction amount of the magnetic recording medium ontowhich the aforementioned carbon protective film 63 is formed, wasmeasured according to the corrosion test described in the following

[0592] The test comprised the steps of allowing the aforementionedmagnetic recording medium to sit for 96 hours at a high temperature (60°C.) and high humidity (80%); subsequently soaking the medium in 50 cc ofultrapure water for 30 minutes; and then measuring the amount of Coextracted in the pure water Additionally, another test was alsoperformed in the same manner with the exception that the aforementionedmagnetic recording medium was instead allowed to sit at a normaltemperature (25° C.) and normal humidity (50%) for 96 hours The testresults are shown in Table 14

[0593] The results of Raman spectral analysis (argon ion laserexcitation), performed on the aforementioned magnetic recording medium,using a Raman spectral analysis apparatus (manufactured by JEOL), arealso shown in Table 14

[0594] Additionally, the hardness of the carbon protective film 63 ofthe aforementioned magnetic recording medium was measured using apico-indentor (manufactured by Hysitron) These results are also shown inTable 14

Test Example 93

[0595] A magnetic recording medium, in which a carbon protective filmcomprising carbon was formed according to the conventionally known,spatter-coating method, using a target comprising carbon, wasmanufactured

[0596] At this time, argon (Ar) was used as the spatter gas, and itsflow rate was set at 90 sccm.

Test Example 94

[0597] A carbon protective film was formed according to theconventionally known, spatter-coating method, using a target comprisingcarbon. At this time, a mixed gas of Ar and nitrogen was used as thespatter gas, and their flow rates were set at 100 sccm, and 50 sccm,respectively Accordingly, the protective film comprised nitrogen andcarbon.

[0598] The above-described corrosion test and Raman spectral analysiswere performed on each magnetic recording medium In addition, thehardness of each magnetic recording medium was measured The results areshown in Table 14. TABLE 13 Protective Bias conditions film Reactant gasPlasma RF Pulse Voltage/ coating Toluene Hydrogen electrical Frequencywidth electrical method (sccm) (sccm) power (W) Type (kHz) (ns) powerTest pCVD 10 240 300 DC 200 500 −100 V Example 89 method Test pCVD 10120 500 RF 400 — 50 W Example 90 method Test pCVD 10 120 500 DC 200 500−100 V Example 91 method Test pCVD 10 120 500 RF 400 — 30 W Example 92method Test Spattering — — — — — — — Example 93 method Test Spattering —— — — — — — Example 94 method

[0599] TABLE 14 Co Co extraction extraction amount amount Raman spectral(60° C. (25° C. analysis Hard- Coating 80%) 50%) νG-line ness rate(ng/cm²) (ng/cm²) (cm⁻¹) Id/Ig (Gpa) (Å/min) Test 0.76 0.38 1543.8 0.5526.6 458 Example 89 Test 0.53 0.38 1556.2 0.90 24.7 409 Example 90 Test1.21 0.49 1541.9 0.66 20.5 753 Example 91 Test 1.47 0.55 1532.2 0.5019.8 789 Example 92 Test 3.39 1.04 1572.3 4.14 10.3 — Example 93 Test4.47 1.19 1561.8 2.95 11.8 — Example 94

[0600] From Tables 13 and 14, the magnetic recording media, in which acarbon protective film was formed according to the plasma CVD method,and wherein the Co extraction amount to substrate area (at 60° C. and80% humidity) was 3 ng/cm2 or less, showed a G-band peak at a higherfrequency, exhibited a smaller Id/Ig, and displayed an increasedhardness due to the effects of DLC, compared to the other magneticrecording media.

[0601] As explained in the aforementioned, according to the presentinvention, it is possible to form a carbon protective film with asuperior durability As a result, it is possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss.

[0602] Therefore, it is possible to provide a highly reliable magneticrecording medium, which is capable of sufficiently increasing therecording density without lowering the output properties thereof.

[0603]FIG. 9 shows the texture-processing equipment used in anotherembodiment of the method for manufacturing magnetic recording mediumaccording to the present invention

[0604] The texture-processing equipment shown herein is provided with asubstrate support member 24, which supports the non-magnetic substrate Sfor texture-processing in a manner such that it can rotate; abrasivetape supply members 25 and 25, which supply abrasive tape A tomechanically scrape the non-magnetic substrate S, contact rollers 26 and26, which press the abrasive tape A against one area of the surface ofthe substrate S, and abrasive particle supply nozzles 27 and 27 whichsupply abrasive particles to the area of contact between the abrasivetape A and substrate S.

[0605] The abrasive tape supply member 25 is provided with a deliveryroll 25 a, which sends the abrasive tape A out, and a receiving roll 25b, which receives the abrasive tape A. The aforementioned supply member25 comprises a structure in which the abrasive tape A, wound arounddelivery roll 25 a, may be received by receiving roll 25 b, at any speedin the direction perpendicular to the radial direction of the substrateS, where the abrasive tape A is in contact with the substrate S Anabrasive tape supply member 25 is provided on each side of the substrateS.

[0606] Additionally, the abrasive tape supply member 25 is preferablydesigned such that the abrasive tape A is able to oscillate in adirection approximately perpendicular to the running direction of thetape.

[0607] In addition, it is possible to design the aforementionedsubstrate support member 24 such that it is able to oscillate in adirection approximately perpendicular to the running direction of thetape, in order so that the substrate S is able to oscillate against theabrasive tape A.

[0608] The contact rollers 26 may comprise a synthetic resin, rubber,metal, and the like, and are provided on each side of the substrate S,such that the roller 26 lies in contact with the substrate S, via theabrasive tape A, in a direction approximately perpendicular to therunning direction of the tape

[0609] The outer diameter of the contact roller 26 is preferably in therange of 20˜100 mm, and the length in the axial direction is preferablyset at a length which reaches the most-outer circumference from themost-inner circumference on the surface of the substrate S to undergoabrasion at the time of texture-processing.

[0610] The contact roller 26 is preferably attached in the direction ofthe substrate S such that the aforementioned abrasive tape is pushedagainst the substrate S with a predetermined pressure such as 0.3˜4kg/cm².

[0611] Examples of the abrasive tape A may include conventionally used,polishing tape, texture tape, and wiping tape, in particular, tapes witha thickness of 0.1˜1.0 mm and width of 20˜60 mm are preferred

[0612] The abrasive supply nozzle 27 is provided at the upper portion ofthe contact roller 26 such that abrasive particle slurry in the abrasiveparticle slurry tank (not shown) can be introduced to the area ofcontact between the abrasive tape A and substrate S

[0613] In the following, another embodiment of the aforementioned methodfor manufacturing magnetic recording medium according to the presentinvention is described, using an example in which the aforementionedtexture-processing equipment and plasma CVD apparatus shown in FIG. 1are employed

[0614] Initially, the non-magnetic substrate S is supported by asubstrate support member 24 of the texture-processing equipment.

[0615] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for magnetic recording medium, examples ofwhich may include an aluminium alloy substrate coated with a NiP metalfilm, and substrates comprising glass, silicone, and the like.

[0616] The substrate S is rotated in the direction shown by the arrow inthe figure at a predetermined speed.

[0617] The rotational speed of the substrate S is preferably in therange of 300˜2000 rpm. A rotational speed less than 300 rpm results in areduction in the efficiency of texture-processing, while a rotationalspeed exceeding 2000 rpm tends to result in a non-uniform, processedsurface for the substrate.

[0618] The abrasive tape A set in the abrasive tape supply member 25 isreceived by means of the receiving roll 25 b. The speed at which theabrasive tape A is received preferably lies in the range of 0.1˜2cm/sec.

[0619] The abrasive tape A runs over the substrate S while in contactwith both sides of the substrate S, at the time of passing between thecontact roller 26 and substrate S

[0620] At the same time, an abrasive particle slurry stored in theabrasive particle slurry tank (not shown) is introduced and allowed torun onto the abrasive tape A, via the abrasive particle supply nozzle27.

[0621] The aforementioned abrasive particle slurry comprises a slurry inwhich abrasive particles are suspended in water.

[0622] The abrasive particle may comprise any particle that isconventionally used in texture-processing, examples of which may includediamond abrasive particles, alumina abrasive particles, carbon siliconabrasive particles, and the like Among the aforementioned, diamondabrasive particles are particularly preferred. The average particlediameter is preferably in the range of 0 1˜0 5 μm

[0623] If the average particle diameter is less than 0.1 μm, theresultant abrasion tends to be inadequate, while an average diameterexceeding 0 5 μm tends to result in the surface of the substratebecoming too rough, both of which are undesirable

[0624] As the abrasive particle slurry, the aforementioned abrasiveparticles are preferably added to water to comprise approximately 5˜30%.In addition, the flow rate of the abrasive particle slurry is preferablyin the range of 10˜100 ml/min.

[0625] The abrasive particle slurry introduced from the abrasiveparticle supply nozzle 27 reaches the area of contact between theabrasive tape A and substrate S. Here, the abrasive particles in theabrasive particle slurry are rubbed onto the substrate S, by means ofrunning the abrasive tape A in the direction perpendicular to the radialdirection of the substrate S, to scrape the surface of the substrate S.By means of scraping the surface of the rotating substrate S withabrasive particles, the resultant grooves are formed on the surface ofthe substrate in the running direction of the abrasive tape A, i.e.,approximately, along the periphery of the substrate S.

[0626] In the method for manufacturing magnetic recording mediumaccording to the present embodiment, the aforementioned operation iscontinued until the average surface roughness of the substrate S (Ra)becomes 1˜20 Å If the average surface roughness of the substrate S (Ra)is less than 1 Å, the resultant magnetic recording medium becomesexcessively flat, leading to an inferior CSS property, If it exceeds 20Å, the surface of the resultant magnetic recording medium becomes tooirregular, leading to a deterioration in the glide avalanche property

[0627] In addition, when performing texture-processing, it is preferableto oscillate the abrasive tape A in the direction perpendicular to therunning direction of the tape by means of the aforementioned oscillationmechanism, to treat the processing surface of the substrate S uniformlyin the radial direction of the substrate. The frequency of oscillationis preferably in the range of 0.1˜5 Hz.

[0628] In addition, the width of the abrasive tape A at the time ofoscillation is preferably in the range of 0.1˜30 mm.

[0629] Furthermore, the direction of oscillation of the abrasive tape Ais not limited to a direction perpendicular to the running direction ofthe tape, so long as the direction crosses the running direction of thetape

[0630] Subsequently, using conventional spatter equipment or the like, anon-magnetic base film and magnetic film are formed on a substrate S,which has been treated with texture-processing, to obtain a disc D. Thematerial and thickness of the non-magnetic base film and magnetic filmare as described in the aforementioned.

[0631] The formation of the aforementioned non-magnetic base film andmagnetic film is not limited to spatter-coating, but may also be carriedout in accordance with vacuum evaporation, ion plating, metal plating,and the like.

[0632] Subsequently, the disc D is transported into the chamber 10 ofthe plasma CVD apparatus shown in FIG. 1, and the surface of the disc Dis exposed to a reactant gas, which is supplied from the supply source14 through the introduction tube 15 into the chamber 10, from which thegas is exhausted via the exhaust tube 16 to circulate the gas within.

[0633] The reactant gas is preferably a mixed gas of hydrocarbon andhydrogen, with a mixing ratio of hydrocarbon to hydrogen in the range of2 to 1˜1 to 100 by volume The hydrocarbon preferably comprises at leastone type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons

[0634] In this operation, the flow rate of the reactant gas ispreferably in the range of 50˜500 sccm Additionally, the inner pressureof the chamber 10 is maintained at a predetermined value such as 0 1˜100Pa

[0635] At the same time, high frequency electrical power of preferably500-2000 W is supplied to the electrodes 11 to generate plasma, and acarbon protective film is formed on both sides of the disc D by means ofplasma chemical gas phase growth, using the aforementioned reactant gasas a starting material. The thickness of the carbon protective film ispreferably in the range of 30˜100 Å

[0636] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied to eachelectrode different. By means of making the phases of electrical powersupplied to each electrode 11 different, it is possible to improve boththe coating rate and durability of the protective film The difference inthe phase of electrical power supplied to each electrode is preferablyin the range of 90˜270°, and in particular, the opposite phase (i e,180°) is preferred

[0637] It is preferable to form the film while performing bias applyingsuch as high frequency bias or pulse D C bias to the disc D, using thebias electrical source 13

[0638] The conditions of bias such as voltage and the like arepreferably as described in the aforementioned.

[0639] The resultant carbon protective film contains a higher content ofdiamond-like-carbon (DLC), which exhibit an increased hardness.

[0640] Additionally, it is possible to provide a lubricating film bymeans of applying the aforementioned lubricant on the protective film.

[0641] Examples of the magnetic recording medium manufactured accordingto the aforementioned manufacturing method may include a magneticrecording medium comprising a structure shown in FIG. 2.

[0642] In the magnetic recording medium according to this embodiment, anon-magnetic substrate S, a non-magnetic base film 31, a magnetic film32, a carbon protective film 33, and a lubricating film 34 are provided.

[0643] According to the aforementioned manufacturing method, a carbonprotective film is formed by means of a plasma CVD method, after anon-magnetic base film and magnetic film are formed on the substrate S,which has been treated with texture-processing In this manner, thecarbon protective film contains a high content of DLC, leading to asuperior durability. Accordingly, it is possible to make the carbonprotective film thinner while also maintaining a sufficient durability.

[0644] Consequently, the surface of the resultant magnetic recordingmedium reflects the surface of the substrate S, wherein the averagesurface roughness (Ra) is in the range of 1˜20 Å, while also maintaininga uniform and sufficient difference in height.

[0645] Accordingly, it is possible to provide a highly reliable magneticrecording medium exhibiting superior CSS and glide avalanche properties,which is capable of sufficiently increasing the recording densitywithout lowering the output properties thereof

[0646] On the other hand, when the carbon protective film is formedaccording to a conventional spatter-coating method or the like, thethickness of the carbon protective film must be increased to a certainextent, from the perspective of the resistance to sliding Therefore,even if the irregularities on the surface of the substrate S areuniform, the micro-irregularities on the surface of the magneticrecording medium tend to become non-uniform Moreover, when the averagesurface roughness of the substrate S (Ra) is kept low, for example inthe range of 1˜20 Å, in order to increase the glide avalanche property,the magnetic head adherence during the CSS operation tends to occur dueto the partially flat surface of the magnetic recording medium, thusleading to inferior CSS properties.

[0647] In the following, the effects of the present invention arespecified, using concrete examples.

Test Example 95

[0648] A magnetic recording medium was manufactured using the plasma CVDapparatus and texture-processing equipment shown in FIGS. 1 and 3,respectively. The texture-processing equipment (manufactured by Hitachi)is provided with a controller 26 comprising rubber with an outercircumference of 42 mm and length in axial direction of 42 mmAdditionally, 2501-2 manufactured by Chiyoda (with a thickness of 0 2 mmand width of 38 mm) was used as the abrasive tape A

[0649] An aluminium alloy substrate S coated with a NiP metal film (witha diameter of 95 mm, and thickness of 0.8 mm) was supported by means ofa substrate support member 24 of the texture-processing equipment, androtated at a constant speed of 380 rpm, while the abrasive tape A waspushed against and ran over the substrate S with a pressure of 2 kg/cm²At the same time, the abrasive particle slurry was introduced from theabrasive particle supply nozzle 27, to supply abrasive particles betweenthe abrasive tape A and substrate S

[0650] The receiving speed of the abrasive tape A was set at 0 2 cm/secFurthermore, a 20% mixed solution of diamond abrasive particles with aparticle diameter of 0 3 μm was used as the abrasive particle slurry.Additionally, when performing texture-processing, the abrasive tape Awas oscillated at a frequency of 2 Hz and oscillation width of 20 mm, inthe direction perpendicular to the running direction of the tape, bymeans of an oscillation mechanism (not shown)

[0651] The average surface roughness (Ra) of the substrate S as a resultof this texture-processing operation is shown in Table 15

[0652] A non-magnetic base film comprising a Cr alloy (with a thicknessof 600 Å), and a magnetic film comprising a Co alloy were successivelyformed on the resultant substrate S by means of DC Magnetron Spatteringdevice (3010 manufactured by Anelva), to form a disc D

[0653] Subsequently, the disc D was transported into the chamber 10 ofthe plasma CVD apparatus, and a reactant gas was supplied from thesupply source 14 into the chamber to achieve a flow rate of 130 sccm. Amixed gas of toluene and hydrogen, with a mixing ratio of toluene tohydrogen of 1 to 10 by volume, was used as the reactant gas. Inaddition, the inner pressure of the chamber 10 was maintained at 6 Pa

[0654] At the same time, high frequency electrical power of 500 W wassupplied to the electrodes 11 to generate plasma, and a carbonprotective film with a thickness of 50 Å was formed on both sides of thedisc D. High frequency electrical power of 50 W was applied to the discD, using the bias electrical source 13. Additionally, the difference inthe phase of high frequency electrical power supplied to each electrode11 was set at 180°.

[0655] Subsequently, a lubricating film with a thickness of 15 Å wasformed by means of applying a fomblin lubricant onto the carbonprotective film, thereby yielding a magnetic recording medium

[0656] The glide avalanche test, and CSS test described in the followingwere performed on the magnetic recording medium.

[0657] In the glide avalanche test, the glide avalanche of the magneticrecording medium was measured using a grind tester (DS4200 manufacturedby Sony Techtronics)

[0658] In addition, in the CSS test, using an MR head, a CSS operationwas performed 20000 times at a rotational speed of 7200 rpm, and atemperature of 40° C. with a humidity of 80%. The dynamic stiction valuewas monitored after allowing the magnetic recording medium to sit forone hour. These results are shown in Table 15

Test Examples 96˜99

[0659] Magnetic recording media were manufactured, in which the averagesurface roughness (Ra) of the substrate S was modified by means ofadjusting the duration time for performing texture-processing

[0660] The glide avalanche test and CSS test were performed on thesemagnetic recording media The results are shown in Table 15

Test Examples 100 and 101

[0661] Magnetic recording media were manufactured, in which the averagesurface roughness (Ra) of the substrate S was changed by means ofmodifying the particle diameter of the abrasive particles used intexture-processing.

[0662] The glide avalanche test and CSS test were performed on thesemagnetic recording media The results are shown in Table 15

Test Example 102

[0663] A magnetic recording medium was manufactured in the same manneras in Test Example 96, with the exception that the carbon protectivefilm was formed according to the spatter-coating method.

[0664] The glide avalanche test and CSS test were performed on thismagnetic recording medium The results are shown in Table 15. TABLE 15Number Average of rotation Abrasive surface Glide Oscillation ofparticle rough- ava- Stic- frequency substrate diameter ness lanche tion(Hz) (rpm) (μm) Ra (Å) (μinch) (−) Test Ex- 3 380 0.3 9 0.26 0.37 ample95 Test Ex- 3 450 0.3 17 0.30 0.34 ample 96 Test Ex- 3 300 0.3 18 0.320.40 ample 97 Test Ex- 5 300 0.3 20 0.33 0.31 ample 98 Test Ex- 3 2000 0.3 12 0.29 0.36 ample 99 Test Ex- 3 450 1.0 28 0.51 0.36 ample 100 TestEx- 3 600 1.0 30 0.56 0.39 ample 101 Test Ex- 3 450 0.3 17 0.40 0.97ample 102

[0665] From the results shown in Table 15, it is clear that the magneticrecording media manufactured according to the plasma CVD method, whereinthe average surface roughness (Ra) was 1˜20 Å, exhibited sufficientlylow glide avalanche values and stiction values, leading to superior CSSand glide avalanche properties

[0666] As explained in the aforementioned, according to the presentinvention, it is possible to provide a highly reliable magneticrecording medium exhibiting superior CSS and glide avalanche properties,which is capable of increasing the recording density sufficientlywithout lowering the output properties thereof

[0667] In the following, another embodiment of the method formanufacturing magnetic recording medium according to the presentinvention is described, using an example in which the plasma CVDapparatus shown in FIG. 1 is employed

[0668] Initially, a non-magnetic base film and magnetic film are formedon both sides of a non-magnetic substrate, according to thespatter-coating method, to obtain a disc D

[0669] The non-magnetic substrate may comprise any substrate that isgenerally used as a substrate for magnetic recording medium, asdescribed in the aforementioned

[0670] The surface of the non-magnetic substrate is preferably treatedwith texture-processing such as mechanical texture-processing. Inparticular, the average surface roughness (Ra) is preferably in therange of 1˜20 Å. If the Ra exceeds 20 Å, the grind height property ofthe resultant magnetic recording medium is undesirably reduced. Thematerials and thickness of the non-magnetic base film and magnetic filmare as described in the aforementioned.

[0671] Subsequently, the disc D, provided with the non-magnetic basefilm and magnetic film on the non-magnetic substrate according to theaforementioned operation, is transported into the chamber 10 of theplasma CVD apparatus, and the surface of the disc D is exposed to areactant gas, which is supplied from the supply source 14 through theintroduction tube 15 into the chamber 10. Gas is exhausted via theexhaust tube 16 from chamber 10 to circulate the gas within.

[0672] In the manufacturing method according to the present embodiment,the reactant gas is preferably a butadiene gas or a mixed gas ofbutadiene and hydrogen which mixing ratio of butadiene to hydrogen ispreferably in the range of 100 to 0˜1 to 100 by volume, and morepreferably 100 to 0˜1 to 25

[0673] If the mixing ratio of butadiene in the aforementioned gas byvolume is less than the aforementioned range, the coating rate becomestoo low, unsuitable for practical industrial production.

[0674] Additionally, when using the aforementioned mixed gas ofbutadiene and hydrogen as the reactant gas, the mixing ratio ofbutadiene to hydrogen in the reactant gas is preferably in the range of100 to 60˜1 to 100, and more preferably 100 to 60˜1 to 25.

[0675] When forming the carbon protective film, the inner pressure ofthe chamber 10 is preferably set at a predetermined value, such as 01˜10 Pa

[0676] At the same time, high frequency electrical power of preferably50˜2000 W is supplied to the electrodes 11, using the high frequencyelectrical source 12, to generate plasma, and a carbon protective filmis formed on both sides of the disc D by means of plasma chemical gasphase growth, using the aforementioned reactant gas as a startingmaterial Herein, the aforementioned butadiene gas serves as the carbonsource for the carbon protective film

[0677] When supplying electrical power to the electrodes 11 and 11, itis preferable to make the phases of electrical power supplied,to eachelectrode 11 different. By means of making the phases of electricalpower supplied to each electrode 11 different, it is possible to improvethe coating rate and durability of the protective film. The differencein the phase of electrical power supplied to each electrode ispreferably in the range of 90˜270°, and in particular, the oppositephase (i.e., 180°) is preferred

[0678] The thickness of the carbon protective film is in the range of30˜100 Å, and preferably 30˜75 Å. If the thickness is less than theaforementioned range, the resistance to corrosion of the resultantcarbon protective film is decreased If the thickness exceeds theaforementioned range, the resultant magnetic recording medium tends to(undesirably) exhibit greater spacing loss at the time of recording andreplay.

[0679] At the time of forming the carbon protective film, bias such ashigh frequency bias and pulse D C. bias, is applied to the disc D, usingthe electrical bias source 13

[0680] When using high frequency bias as the bias, high frequencyelectrical source is used as the bias electrical source 13, and highfrequency electrical power of 10˜300 W, preferably 10˜150 W, is appliedto the disc D

[0681] If the electrical power is less than the aforementioned range,the resistance to sliding of the resultant carbon protective film isreduced If the electrical power exceeds the aforementioned range,abnormal discharge tends to occur in the chamber 10 at the time ofcoating, leading undesirably to portions of abnormal growth on thecarbon protective film

[0682] When using pulse D C. bias as the bias, a pulse D C electricalsource is used as the bias electrical source 13, and a voltage of−400˜−10 V, preferably −300˜−50 V is applied to the disc D

[0683] If the voltage is less than the aforementioned range, resistanceto sliding of the obtained, carbon protective film is reduced If itexceeds the aforementioned range, abnormal discharge tends to occur inthe chamber 10 during coating, leading undesirably to portions ofabnormal growth on the carbon protective film

[0684] Additionally, the pulse width of the aforementioned pulse D Cbias is preferably in the range of 10˜50000 ns, and the frequency ispreferably in the range of 10 kHz˜1 GHz

[0685] By means of performing bias applying, the carbon protective filmcontains a higher content of diamond-like-carbon (DLC), which exhibitboth an increased hardness and superior strength.

[0686] Additionally, a lubricating film may be provided on theprotective film, by means of applying the aforementioned lubricant

[0687] In the aforementioned manufacturing method, by means of using abutadiene gas, or a mixed gas of butadiene and hydrogen, which mixingratio of butadiene to hydrogen is in the range of 100 to 0˜1 to 100 byvolume, as the reactant gas, at the time of forming the carbonprotective film, it is possible to form a carbon protective film with asuperior durability. As a result, it is possible to make the carbonprotective thinner while maintaining the durability, and to provide amagnetic recording medium that is capable of reducing spacing loss

[0688] Consequently, it is possible to provide a highly reliablemagnetic recording medium, which is capable of sufficiently increasingthe recording density without lowering the output properties thereof.

[0689] Additionally, by means of performing bias applying to the disc Dat the time of forming the carbon protective film, the carbon protectivefilm contains a higher content of DLC, leading to a superior strength Inaddition, it is also possible to improve the coating rate, leading to anefficient production.

[0690] The reason that the carbon protective film with a superiordurability can be provided by means of using a butadiene gas, or a mixedgas of butadiene and hydrogen, which mixing ratio of butadiene tohydrogen is in the range of 100 to 0˜1 to 100 by volume, as the reactantgas when forming the aforementioned carbon protective film, is unclearHowever, this may be attributable to the fact that the resultant carbonprotective film contains a higher content of DLC which exhibit anexcellent hardness, and thus displays an overall superior strength, bymeans of using the aforementioned gas as the reactant gas

[0691] A mixed gas wherein other gases such as nitrogen, argon, oxygen,fluorine, and the like, are added into the aforementioned butadiene gas,or mixed gas of butadiene and hydrogen at a mixing ratio of for example1˜100 vol %, may be also used as the reactant gas

[0692] In addition, a mixed gas wherein other gases, which may serve asa carbon source, such as methane, ethane, ethylene, propylene, butylene,butane, benzene, toluene, and the like, are mixed into butadiene gas ata mixing ratio of, for example, 1˜100 vol %, may be used instead of theaforementioned butadiene gas.

[0693] In addition, in the aforementioned manufacturing method accordingto the present embodiment, a carbon protective film is formed accordingonly to a plasma CVD method. However, the method for manufacturingmagnetic recording medium according to the present invention is notlimited thereto, and a protective film may also comprise a multi-layerstructure comprising a plasma carbon layer formed according to theplasma CVD method, and a layer formed according to another method, suchas a spatter-carbon layer and/or tantalic nitride layer formed accordingto the spattering method.

[0694] In the following, the effects of the present invention arespecified, using concrete examples.

Test Example 103˜117

[0695] After an aluminium alloy substrate coated with a NiP metal film(with a diameter of 95 mm and thickness of 0 8 mm) was treated withmechanical texture-processing to form an average surface roughness of 20Å, a non-magnetic base film (with a thickness of 600 Å) comprising a Cralloy, and a magnetic film comprising a Co alloy were successivelyformed on both sides of the substrate S, using DC Magnetron SpatterEquipment (3010 manufactured by Anelva), to obtain a disc DSubsequently, the disc D was transported into the chamber 10 of theplasma CVD apparatus, and the reactant gas was supplied from the supplysource 14 inside of the chamber

[0696] At the same time, high frequency electrical power of 700 W (witha frequency of 13 56 MHz) was supplied to the electrodes 11, to generateplasma, and a carbon protective film with a thickness of 50A was formedon both sides of the disc D

[0697] The temperature of the disc D when forming the carbon protectivefilm was set at 160° C. The distance between the electrodes 11 and discD was set at 30 mm The inner pressure of the chamber was maintained at 2Pa

[0698] The type and flow rate of the reactant gas, type and power ofbias applied to the disc D by means of the bias electrical source 13,difference in the phase of high frequency electrical power supplied tothe electrodes 11, thickness of the formed carbon protective film, andcoating rate are shown in Table 16.

[0699] Subsequently, a lubricating film with a thickness of 20 Å wasformed on the carbon protective film by means of applying a fomblinlubricant, thereby yielding a magnetic recording medium.

[0700] The CSS test, corrosion test, and Raman spectral analysisdescribed in the following were performed on the resultant magneticrecording media.

[0701] In the CSS test, using an MR head, a CSS operation was performed20000 times at a rotational speed of 7200 rpm, and a temperature of 40°C. with a humidity of 80%. The dynamic stiction value was monitoredafter allowing the magnetic recording medium to sit for one hour

[0702] In the corrosion test, after being allowed to sit for 96 hours ata high temperature (60° C.) and a high humidity (80%), the magneticrecording medium was soaked in 50 cc of ultrapure water at 25° C., andthe extraction amount of Co (per substrate area) was measured Inaddition, after being allowed to sit for 96 hours at a normaltemperature (25° C.) and normal humidity (50%), the extraction amount ofCo was measured in the same manner

[0703] In the Raman spectral analysis, Raman spectral analysis (argonion laser excitation) was performed, using a Raman spectral analysisapparatus (manufactured by JEOL) The results are shown in Table 17

[0704] In the table, “RF” represents high frequency Furthermore, “RFphase difference” represents the difference in the phase of electricalpower supplied to two electrodes 11 and 11 TABLE 16 Reactant gas Carbonsource Ratio of gas Hydrogen butadiene RF Protective Flow flow inreactant phase film Coating rate rate gas Bias difference thickness rateType (sccm) (sccm) (vol. %) Bias power (°) (Å) (Å/min) Test Ex 103 Buta-6 120 4.8 Pulse −200 V 180 50 218 diene D.C. Test Ex 104 Buta- 30 20013.0 Pulse −200 V 180 50 285 diene D.C. Test Ex 105 Buta- 30 120 20.0Pulse −200 V 180 50 533 diene D.C. Test Ex 106 Buta- 30 120 20.0 RF  30W 180 50 506 diene Test Ex 107 Buta- 25 60 29.4 Pulse −200 V 180 50 552diene D.C. Test Ex 108 Buta- 30 20 60.0 Pulse −200 V 180 50 689 dieneD.C. Test Ex 109 Buta- 30 0 100 Pulse −200 V 180 50 810 diene D.C. TestEx 110 Buta- 3 120 2.4 Pulse −200 V 180 50 165 diene D.C. Test Ex 111Buta- 30 120 20.0 None  — 180 50 386 diene Test Ex 112 Buta- 30 120 20.0Pulse −200 V 0 50 185 diene D.C. Test Ex 113 Buta- 30 120 20.0 Pulse−200 V 180 20 533 diene D.C. Test Ex 114 Methane 60 60 — Pulse −200 V180 50 324 D.C Test Ex 115 Ethane 100 0 — Pulse −200 V 180 50 385 D.C.Test Ex 116 Ethylene 60 60 — Pulse −200 V 180 50 308 D.C. Test Ex 117Acetone 100 0 — Pulse −200 V 180 50 221 D.C.

[0705] TABLE 17 Corrosion test Normal temp. High temp. Raman spectral &normal & high analysis Stiction humidity humidity νG-line Id/Ig (−)(μg/disc) (μg/disc) (cm⁻¹) (−) Test 0.64 0.05 0.11 0.44 1540.5 Example103 Test 0.81 0.07 0.17 0.38 1536.7 Example 104 Test 0.43 0.08 0.22 0.371538.2 Example 105 Test 0.60 0.04 0.16 0.40 1536.4 Example 106 Test 0.960.08 0.20 0.36 1534.8 Example 107 Test 0.77 0.08 0.24 0.35 1533.9Example 108 Test 0.71 0.08 0.18 0.34 1533.8 Example 109 Test 0.88 0.070.13 0.48 1541.2 Example 110 Test Crash 0.36 0.99 no peak — Example 111Test 0.56 0.21 0.77 0.75 1539.5 Example 112 Test 1.23 0.78 2.57 — —Example 113 Test 2.25 0.11 0.45 1.02 1558.0 Example 114 Test Crash 0.140.58 0.35 1559.6 Example 115 Test 2.12 0.16 0.36 — — Example 116 TestCrash 0.23 0.74 — — Example 117

[0706] From the results shown in Tables 16 and 17, it is clear that themagnetic recording media manufactured according to the method whereinbias was applied to the disc D at the time of coating, and butadiene gasor a mixed gas of butadiene and hydrogen, with a mixing ratio ofbutadiene to hydrogen of 100 to 0˜1 to 100 by volume, exhibited lowerstiction values, leading to a superior resistance to the CSS operationAdditionally, it is clear that the coating rate improved

[0707] In addition, from the results of the corrosion test, theaforementioned magnetic recording media displayed an extremely smallamount of corrosion, and exhibited a resistance to corrosion to a degreewhich poses no problems from practical use Additionally, from theresults of the Raman spectral analysis, the aforementioned magneticrecording medium exhibited a G-band peak of a relatively higherfrequency, a low Id/Ig, and a high DLC content

[0708] In addition, the magnetic recording medium manufactured accordingto the method wherein the difference in the phase of high frequencyelectrical power supplied to the electrodes 11 was 180 degrees, resultedin an improvement in the coating rate, compared to those with nodifference in the phase.

[0709] As explained in the aforementioned, according to the method formanufacturing magnetic recording medium according to the presentinvention, it is possible to form a carbon protective film with asuperior durability As a result, it is possible to make the carbonprotective film thinner while also maintaining a sufficient durability,and thereby reduce spacing loss.

[0710] Accordingly, it is possible to provide a highly reliable magneticrecording medium which is capable of sufficiently increasing therecording density without lowering the output properties thereofadditionally, it is possible to increase the coating rate, leading to anefficient production Industrial Applicability

[0711] the magnetic recording medium and method for manufacturing thesame according to the present invention may be applied to a magneticrecording medium (and manufacturing method for the same), such asmagnetic disc or the like, which is used in magnetic disc equipment

What is claimed is:
 1. A method for manufacturing a magnetic recordingmedium comprising the steps of forming a carbon protective film onto adisc, the non-magnetic substrate of which is layered with a non-magneticbase film and magnetic film, using a reactant gas containing carbonatoms as a starting material, according to a plasma CVD method, whereina mixed gas of hydrocarbon and hydrogen, in which the mixing ratio ofhydrocarbon to hydrogen is in the range of 2 to 1˜1 to 100 by volume, isused as a reactant gas, while applying a bias to said disc.
 2. A methodfor manufacturing a magnetic recording medium according to claim 1,wherein toluene is used as said hydrocarbon.
 3. A method formanufacturing a magnetic recording medium according to claim 2, whereina mixed gas of toluene and hydrogen, in which the mixing ratio oftoluene and hydrogen is in the range of 1 to 15˜1 to 20 by volume, isused as said reactant gas
 4. A method for manufacturing a magneticrecording medium according to one of claims 1˜3, wherein high frequencybias is used as said bias.
 5. A method for manufacturing a magneticrecording medium according to one of claims 1˜3, wherein said carbonprotective film is formed according to a plasma CVD method, under highfrequency electrical discharge.
 6. A method for manufacturing a magneticrecording medium according to claim 4, wherein said carbon protectivefilm is formed according to a plasma CVD method, under high frequencyelectrical discharge
 7. A method for manufacturing a magnetic recordingmedium according to claim 5, wherein the phases of electrical power,supplied to each electrode arranged on the respective sides of saiddisc, are different from each other at the time of forming said carbonprotective film simultaneously, on both sides of said disc, under highfrequency electrical discharge.
 8. A method for manufacturing a magneticrecording medium according to claim 6, wherein the phases of electricalpower, supplied to each electrode arranged on the respective sides ofsaid disc, are different from each other, at the time of forming saidcarbon protective film simultaneously, on both sides of said disc, underhigh frequency electrical discharge.
 9. A method for manufacturing amagnetic recording medium comprising the steps of forming a carbonprotective film onto the disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, using areactant gas containing carbon atoms as a starting material, accordingto a plasma CVD method, wherein pulse D.C. bias having a frequency of 1kHz˜100 GHz and pulse width of 1 ns˜500 μs is applied to said disc, atthe time of forming the carbon protective film
 10. A method formanufacturing a magnetic recording medium according to claim 9, whereinsaid pulse D C. bias applied to said disc comprises a frequency of 10kHz ˜1 GHz and pulse width of 10 ns˜50 μs.
 11. A method formanufacturing a magnetic recording medium according to claim 9, whereinsaid pulse D.C. bias applied to said disc comprises an average voltageof −400˜−10 V
 12. A method for manufacturing a magnetic recording mediumaccording to claim 10, wherein said pulse D C. bias applied to said disccomprises an average voltage of −400˜−10 V.
 13. A method formanufacturing a magnetic recording medium according to one of claims9˜12, wherein a mixed gas of hydrocarbon and hydrogen, in which themixing ratio of hydrocarbon to hydrogen is in the range of 2 to 1˜1 to100 by volume, is used as said reactant gas during formation of a carbonlayer.
 14. A method for manufacturing a magnetic recording mediumaccording to claim 13, wherein said hydrocarbon comprises at least onetype of hydrocarbon selected from among lower saturated hydrocarbons,lower unsaturated hydrocarbons, and lower cyclic hydrocarbons.
 15. Amagnetic recording medium comprising a carbon protective film formedonto a disc, the non-magnetic substrate of which is layered with anon-magnetic base film and magnetic film, wherein said carbon protectivefilm is formed according to a plasma CVD method, while applying pulse DC. bias, having a frequency of 1 kHz˜100 GHz and pulse width of 1 ns˜500μs to said disc
 16. A method for manufacturing a magnetic recordingmedium comprising the steps of forming a carbon protective film onto adisc, the non-magnetic substrate of which is layered with a non-magneticbase film and magnetic film, using a reactant gas containing carbonatoms as a starting material, according to a plasma CVD method, whereinthe temperature of said disc is set at a temperature in the range of100˜250° C. in advance, at the time of forming said carbon protectivefilm
 17. A method for manufacturing a magnetic recording mediumaccording to claim 16, wherein a mixed gas of hydrocarbon and hydrogen,in which the mixing ratio of hydrocarbon and hydrogen is in the range of2 to 1˜1 to 100 by volume, is used as said reactant gas.
 18. A methodfor manufacturing a magnetic recording medium according to claim 17,wherein said hydrocarbon comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons
 19. A method formanufacturing a magnetic recording medium comprising the steps offorming a carbon protective film onto a disc, the non-magnetic substrateof which is layered with a non-magnetic base film and magnetic film,using a reactant gas containing carbon atoms as a starting material,according to a plasma CVD method, wherein the pressure of said reactantgas is set in the range of 0.1˜10 Pa.
 20. A method for manufacturing amagnetic recording medium according to claim 19, wherein the pressure ofsaid reactant gas is set in the range of 2˜6 Pa.
 21. A method formanufacturing a magnetic recording medium according to one of claims 19and 20, wherein a mixed gas of hydrocarbon and hydrogen, in which themixing ratio of hydrocarbon and hydrogen is in the range of 2 to 1˜1 to100 by volume, is used as said reactant gas
 22. A method formanufacturing a magnetic recording medium according to claim 21, whereinsaid hydrocarbon comprises at least one type of hydrocarbon selectedfrom among lower saturated hydrocarbons, lower unsaturated hydrocarbons,and lower cyclic hydrocarbons
 23. A method for manufacturing a magneticrecording medium comprising the steps of forming a carbon protectivefilm onto a disc, the non-magnetic substrate of which is layered with anon-magnetic base film and magnetic film, using a reactant gascontaining carbon atoms as a starting material, according to a plasmaCVD method, wherein said reactant gas comprises nitrogen and a mixedgas, in which the mixing ratio of hydrocarbon to hydrogen is in therange of 2 to 1˜1 to 100, into which nitrogen gas is added at a addingvolume of 0 1˜100% of said mixed gas
 24. A method for manufacturing amagnetic recording medium according to claim 23, wherein saidhydrocarbon comprises at least one type of hydrocarbon selected fromamong lower saturated hydrocarbons, lower unsaturated hydrocarbons, andlower cyclic hydrocarbons.
 25. A magnetic recording medium comprising anon-magnetic base film, magnetic film, carbon protective film, andlubricating film which are formed onto a non-magnetic substrate, whereinsaid carbon protective film comprises a plasma CVD carbon layer formedaccording to a plasma CVD method, and a spatter carbon layer formedaccording to a spatter-coating method, which is provided in contact withthe lubricating film.
 26. A magnetic recording medium according to claim25, wherein the thickness of said spatter carbon layer is in the rangeof 5˜100 Å
 27. A magnetic recording medium according to one of claims 25and 26, wherein the thickness of said plasma CVD carbon layer is in therange of 30˜10 Å
 28. A method for manufacturing a magnetic recordingmedium comprising the steps of forming a plasma CVD carbon layer onto adisc, the non-magnetic substrate of which is layered with a non-magneticbase film and magnetic film, according to a plasma CVD method, using areactant gas containing carbon atoms as a starting material; forming aspatter carbon layer thereon, according to a spatter-coating methodusing a spatter gas; and forming a lubricating film which lies incontact with said spatter carbon layer
 29. A method for manufacturing amagnetic recording medium according to claim 28, wherein a mixed gas ofhydrocarbon and hydrogen, in which the mixing ratio of hydrocarbon tohydrogen is in the range of 2 to 1˜1 to 100 by volume, is used as saidreactant gas for forming said plasma CVD carbon layer according to aplasma CVD method.
 30. A method for manufacturing a magnetic recordingmedium according to claim 29, wherein said hydrocarbon comprises atleast one type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons.
 31. A method for manufacturing a magnetic recording mediumaccording to one of claims 28˜30, wherein a mixed gas comprising argonand at least one gas selected from among nitrogen, hydrogen, andmethane, in which the mixing ratio to argon is in the range of 0.1˜100vol %, is used as said spatter gas for forming said spatter carbon layeraccording to a spatter-coating method.
 32. A method for manufacturing amagnetic recording medium comprising the steps of forming a carbonprotective film onto a disc, the non-magnetic substrate of which islayered with a non-magnetic base film and magnetic film, according to aplasma CVD method, using a reactant gas containing carbon atoms, andforming a lubricating film in contact with said carbon protective film,wherein said carbon protective film is formed by applying a bias andsubsequently this formation is continued without a bias
 33. A method formanufacturing a magnetic recording medium according to claim 32, whereinsaid bias applied to said disc comprises a pulse D C bias of −400˜10 V,or high frequency bias of 10˜300 W
 34. A method for manufacturing amagnetic recording medium according to claim 32, wherein the thicknessof said carbon layer formed without applying bias to said disc is in therange of 5˜20 Å
 35. A method for manufacturing a magnetic recordingmedium according to claim 33, wherein the thickness of said carbon layerformed without applying bias to said disc is in the range of 5˜20 Å. 36.A method for manufacturing a magnetic recording medium according to oneof claims 32˜35, wherein a mixed gas of hydrocarbon and hydrogen, inwhich the mixing ratio of hydrocarbon to hydrogen is in the range of 2to 1˜1 to 100, is used as said reactant gas for forming said carbonprotective film.
 37. A method for manufacturing a magnetic recordingmedium according to claim 36, wherein said hydrocarbon comprises atleast one type of hydrocarbon selected from among lower saturatedhydrocarbons, lower unsaturated hydrocarbons, and lower cyclichydrocarbons.
 38. A magnetic recording medium comprising a carbonprotective film and lubricating film formed onto a disc, thenon-magnetic substrate of which is layered with a non-magnetic base filmand magnetic film, wherein said carbon protective film comprises a firstcarbon layer, which is formed according to a plasma CVD method whileapplying bias to said disc, and a second carbon layer, which is formedin contact with said lubricating film, according to a plasma CVD method,without applying bias to said disc.
 39. A magnetic recording mediumaccording to claim 38, wherein the thickness of said second carbon layeris in the range of 5˜20 Å
 40. A magnetic recording medium comprising anon-magnetic base film, magnetic film, protective film, and lubricatingfilm which are formed onto a non-magnetic substrate, wherein saidprotective film comprises a tantalum nitrogen layer principallycomprising a material comprising tantalum and nitrogen with a nitrogencontent in the range of 1˜30 at %, and a carbon layer principallycomprising carbon, which is formed in contact with said lubricatingfilm, according to a plasma CVD method.
 41. A magnetic recording mediumaccording to claim 40, wherein the thickness of said carbon layer is inthe range of 5˜100 Å.
 42. A magnetic recording medium according to claim40 or 41, wherein the thickness of said tantalum nitrogen layer is inthe range of 1˜95 Å.
 43. A method for manufacturing a magnetic recordingmedium comprising the steps of forming a non-magnetic base film andmagnetic film onto a non-magnetic substrate; forming a tantalum nitrogenlayer, principally comprising a material in which nitrogen is mixed withtantalum at a mixing ratio of 1˜30 at %, thereon, forming a carbon layerthereon, according to a plasma CVD method, using a reactant gascontaining carbon atoms as a starting material, and forming alubricating film thereon, in contact with said carbon layer
 44. A methodfor manufacturing a magnetic recording medium according to claim 43,wherein a mixed gas of hydrocarbon and hydrogen, in which the mixingratio of hydrocarbon to hydrogen is in the range of 2 to 1˜1 to 100 byvolume, is used as said reactant gas for forming said carbon layer
 45. Amethod for manufacturing a magnetic recording medium according to claim44, wherein said hydrocarbon comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons
 46. A method formanufacturing a magnetic recording medium comprising the steps of:forming a non-magnetic base film and magnetic film onto a non-magneticsubstrate; forming a carbon protective film thereon, according to aplasma CVD method, using a reactant gas containing carbon atoms as astarting material; and forming a lubricating film thereon, wherein priorto formation of said lubricating film, the surface of said carbonprotective film is irradiated with ultraviolet rays.
 47. A method formanufacturing a magnetic recording medium according to claim 46, whereinsaid ultraviolet rays irradiating the surface of said carbon protectivefilm comprise a wavelength of 100˜400 nm.
 48. A method for manufacturinga magnetic recording medium according to claim 46, wherein an excimeremission lamp is used as a source of said ultraviolet rays:
 49. A methodfor manufacturing a magnetic recording medium according to claim 47,wherein an excimer emission lamp is used as a source of said ultravioletrays.
 50. A method for manufacturing a magnetic recording mediumaccording to claim 46, wherein prior to formation of said lubricatingfilm, the surface of said carbon protective film is washed with water.51. A method for manufacturing a magnetic recording medium according toclaim 47, wherein prior to formation of said lubricating film, thesurface of said carbon protective film is washed with water
 52. A methodfor manufacturing a magnetic recording medium according to claim 48,wherein prior to formation of said lubricating film, the surface of saidcarbon protective film is washed with water
 53. A method formanufacturing a magnetic recording medium according to claim 49, whereinprior to formation of said lubricating film, the surface of said carbonprotective film is washed with water.
 54. A method for manufacturing amagnetic recording medium according to one of claims 46˜53, wherein amixed gas of hydrocarbon and hydrogen, in which the mixing ratio ofhydrocarbon to hydrogen is in the range of 2 to 1˜1 to 100 by volume, isused as said reactant gas for forming said carbon protective film.
 55. Amethod for manufacturing a magnetic recording medium according to claim54, wherein said hydrocarbon comprises at least one type of hydrocarbonselected from among lower saturated hydrocarbons, lower unsaturatedhydrocarbons, and lower cyclic hydrocarbons.
 56. A method formanufacturing a magnetic recording medium comprising the steps offorming a non-magnetic base film and magnetic film onto a non-magneticsubstrate, forming a carbon protective film thereon according to aplasma CVD method, using a reactant gas containing carbon atoms as astarting material, and forming a lubricating film thereon; wherein priorto formation of said lubricating film, the surface of said carbonprotective film is washed with water
 57. A method for manufacturing amagnetic recording medium according to one of claim 50˜53, whereinultrapure water is used as the cleaning water for washing said carbonprotective film.
 58. A method for manufacturing a magnetic recordingmedium according to one of claim 56, wherein ultrapure water is used asthe cleaning water for washing said carbon protective film.
 59. Amagnetic recording medium comprising a non-magnetic base film, magneticfilm, carbon protective film, and lubricating film formed onto anon-magnetic substrate, wherein said carbon protective film is formedaccording to a plasma CVD method, after which the surface thereof isirradiated with ultraviolet rays.
 60. A magnetic recording mediumcomprising a non-magnetic base film, magnetic film, carbon protectivefilm, and lubricating film formed onto a non-magnetic substrate, whereinsaid carbon protective film is formed according to a plasma CVD method,using a reactant gas containing carbon atoms, and said lubricating filmprincipally comprises at least one compound selected from among thecompounds represented by the following formula (1)˜(5), the numberaverage molecular weights of which lie in the range of 500˜6000

[wherein m, n, p, q, r, s, t, u, v, and w represent an integer,respectively]
 61. A magnetic recording medium comprising a non-magneticbase film, magnetic film, carbon protective film, and lubricating filmformed onto a non-magnetic substrate, wherein said carbon protectivefilm is formed according to a plasma CVD method, using a reactant gascontaining carbon atoms, and said lubricating film principally comprisesa mixture, in which the compound represented by the following formula(6) is mixed with at least one compound selected from among thecompounds represented by the following formula (1)˜(5), the numberaverage molecular weight of which lie in the range of 500˜6000, at amixing ratio of 0.1˜20 wt %.

[wherein, m, n, p, q, r, s, t, u, v, and w represent an integer,respectively, and x represents an integer between 1 and 6]
 62. Amagnetic recording medium comprising a non-magnetic base film, magneticfilm, carbon protective film, and lubricating film formed onto anon-magnetic substrate, wherein said carbon protective film is formedaccording to a plasma CVD method, using a reactant gas containing carbonatoms, and said lubricating film principally comprises a compoundrepresented by the following formula (1), the number average molecularweight of which is in the range of 500˜6000

[wherein, m and n represent an integer, respectively]
 63. A magneticrecording medium comprising a non-magnetic base film, magnetic film,carbon protective film, and lubricating film formed onto a non-magneticsubstrate, wherein said carbon protective film is formed according to aplasma CVD method, using a reactant gas containing carbon atoms, andsaid lubricating film principally comprises a compound represented bythe following formula (5), the number average molecular weight of whichis in the range of 500˜6000 HO-(CH₂CH₂-O)_(t)-CH₂CF₂O-(CF₂CF₂O)_(u)-(CF₂O)_(u) -CF₂CH₂-(OCH₂CH₂)_(w)-OH   (5)[wherein, t, u, v, and w represent an integer, respectively]
 64. Amagnetic recording medium comprising a non-magnetic base film, magneticfilm containing Co, and carbon protective film formed onto anon-magnetic substrate, wherein said carbon protective film is formedaccording to a plasma CVD method; and the Co extraction amount to thesubstrate area is 3 ng/cm² or less.
 65. A method for manufacturing amagnetic recording medium comprising the steps of: performingtexture-processing on the surface of a non-magnetic substrate to form ansurface average roughness (Ra) of 1˜20 Å, forming a non-magnetic basefilm and magnetic film onto said non-magnetic substrate; and a carbonprotective film thereon according to a plasma CVD method, using areactant gas containing carbon atoms as a starting material
 66. A methodfor manufacturing a magnetic recording medium according to claim 65,wherein said surface average roughness (Ra) of said non-magneticsubstrate is 3˜10 Å when said texture-processing is carried out on saidsurface.
 67. A method for manufacturing a magnetic recording mediumaccording to claim 65, wherein a mechanical texture-processing methodusing abrasive particles is employed as said texture-processing method,and the average particle diameter of said abrasive particles is in therange of 0 1˜0 5 μm.
 68. A method for manufacturing a magnetic recordingmedium according to claim 66, wherein mechanical texture-processingmethod using abrasive particles is employed as a texture-processingmethod, and the average particle diameter of sad abrasive particles isin the range of 0.1˜0.5 μm.
 69. A method for manufacturing a magneticrecording medium according to claim 67, wherein a method, in which thesurface of said non-magnetic substrate undergoes texture-processing bymeans of rotating said non-magnetic substrate while running an abrasivetape on said substrate, in contact with the surface of said non-magneticsubstrate, and supplying abrasive particles between said abrasive tapeand non-magnetic substrate, is employed as said mechanicaltexture-processing method; and said abrasive tape is oscillated in thedirection crossing the running direction of the tape, at a frequency of0 1˜5 Hz.
 70. A method for manufacturing a magnetic recording mediumaccording to claim 68, wherein a method, in which the surface of saidnon-magnetic substrate undergoes texture-processing by means of rotatingsaid non-magnetic substrate while running an abrasive tape on saidsubstrate, in contact with the surface of said non-magnetic substrate,and supplying abrasive particles between said abrasive tape andnon-magnetic substrate, is employed as said mechanicaltexture-processing method, and said abrasive tape is oscillated in thedirection crossing the running direction of the tape, at a frequency of0.1˜5 Hz.
 71. A method for manufacturing a magnetic recording mediumaccording to claim 69, wherein the rotational speed of said non-magneticsubstrate is in the range of 300˜2000 rpm, during texture-processing.72. A method for manufacturing a magnetic recording medium according toclaim 70, wherein the rotational speed of said non-magnetic substrate isin the range of 300˜2000 rpm, during texture-processing.
 73. A methodfor manufacturing a magnetic recording medium according to one of claims65˜72, wherein a mixed gas of hydrocarbon and hydrogen is used as saidreactant gas; and said hydrocarbon comprises at least one type ofhydrocarbon selected from among lower saturated hydrocarbons, lowerunsaturated hydrocarbons, and lower cyclic hydrocarbons.
 74. A magneticrecording medium provided with a non-magnetic base film, magnetic film,and carbon protective film on the non-magnetic substrate, wherein thesurface average roughness (Ra) of said non-magnetic substrate is in therange of 1˜20 Å; and said carbon protective film is formed according toa plasma CVD method.
 75. A method for manufacturing a magnetic recordingmedium comprising the steps of forming a carbon protective film onto adisc, the non-magnetic substrate of which is layered with a non-magneticbase film and magnetic film, according to a plasma CVD method, using areactant gas containing carbon atoms, wherein butadiene gas or a mixedgas of butadiene and hydrogen, in which the mixing ratio of butadiene tohydrogen is in the range of 100 to 0˜1 to 100, is used as said reactantgas, while applying bias to said disc.
 76. A method for manufacturing amagnetic recording medium according to claim 75, wherein a mixed gas ofbutadiene and hydrogen, in which the mixing ratio of butadiene tohydrogen is in the range of 100 to 0˜1 to 25, is used as said reactantgas.
 77. A method for manufacturing a magnetic recording mediumcomprising the steps of exposing a disc, in which both surfaces of thenon-magnetic substrate are layered with a non-magnetic base film andmagnetic film, to a reactant gas containing carbon atoms, whilesupplying electrical power to electrodes arranged on both sides of saiddisc to generate plasma; and forming a carbon protective film on bothsides of said disc, using said reactant gas as a starting material,according to a plasma CVD method, wherein bias is applied to said discat the time of forming said carbon protective film; electrical powersupplied to said electrodes comprises high frequency electrical power;and butadiene gas or a mixed gas of butadiene and hydrogen, in which themixing ratio of butadiene to hydrogen is in the range of 100 to 0˜1 to100, is used as said reactant gas.
 78. A method for manufacturing amagnetic recording medium according to claim 77, wherein the phases ofelectrical power, supplied to each electrode arranged on the respectivesides of said disc, are different from each other, at the time offorming said carbon protective film.
 79. A method for manufacturing amagnetic recording medium according to one of claims 75˜78, wherein thethickness of said carbon protective film is in the range of 30˜100 Å.